pin down

pin down

1. Literally, to use one's body weight to hold someone down on the ground. In this usage, a noun or pronoun can be used between "pin" and "down." My older brother always used to pin me down and pinch my arms when we were kids.
2. By extension, to try to force someone into a position where they must commit to a single, precise answer or piece of information. In this usage, a noun or pronoun can be used between "pin" and "down." The president never let reporters question him long enough for them to pin him down on any issue they brought up. It may seem dishonest, but it's important not to get pinned down on a topic that could hurt the company.
3. To use pins, nails, tacks, etc., to secure or affix something (to something else). In this usage, a noun or pronoun can be used between "pin" and "down." Remember to pin the tarp down, or it will get blown away when the storm hits. Let me just pin down this pattern onto the mannequin so I can remember the design in the morning.
4. To specify something; to establish or determine something concretely. In this usage, a noun or pronoun can be used between "pin" and "down." I'd like to pin down the dates we want to fly so I can start looking at ticket prices. I think we've pinned down the cause of the electrical failures. It seems like you're struggling to pin down what your essay is really trying to say.
See also: down, pin
Farlex Dictionary of Idioms.

pin someone down (on something)

 and nail someone down* (on something)
Fig. to demand and receive a firm answer from someone to some question. (Alludes to shifting from answer to answer; commit to one answer or another.) I tried to pin him down on a time and place, but he was very evasive. Don't try to pin down the mayor on anything! I want to nail her down on a meeting time.
See also: down, pin

pin something down

 and nail something down 
1. Lit to attach or affix something with nails or pins. Pin the pattern down temporarily. Nail down this piece of flooring every 12 inches.
2. Fig. to determine or fix something, such as a date, an agreement, an amount of money, a decision, etc. It will be ready sometime next month. I can't pin the date down just yet, however. I can't pin down the exact date just now.
See also: down, pin
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

pin down

1. Fix or establish clearly, as in The firefighters finally were able to pin down the source of the odor. [Mid-1900s]
2. Force someone to give precise information or opinions, as in The reporter pinned down the governor on the issue of conservation measures. [c. 1700]
See also: down, pin
The American Heritage® Dictionary of Idioms by Christine Ammer.

pin down

v.
1. To secure or fasten something using a pin or pins: The tailor pinned down the patch before sewing it on. I pinned my tie down to stop it from flapping in the wind.
2. To render someone or something immobile by or as if by holding down: We pinned down the tarp with four heavy rocks. They pinned me down on the table while the doctor removed the bullet from my leg. The platoon was pinned down by heavy machine-gun fire.
3. To establish something clearly: Doctors finally pinned down the cause of the disease. I had a strange feeling about the old house, but I couldn't pin it down.
4. To compel someone to give firm opinions or precise information: The reporter pinned the governor down on the issue of raising taxes. The newspaper tried to pin down the candidates on their positions regarding capital punishment.
See also: down, pin
The American Heritage® Dictionary of Phrasal Verbs.
See also:
  • ask down
  • bear down
  • clunk
  • clunk down
  • call down
  • chow down
  • chow something down
  • clean down
  • batter
  • batter down
References in periodicals archive
Impressionism keeps getting harder to pin down. Sept.
Impressionist Still Life
Therefore, while the findings solidify the link between lupus and atherosclerosis, she says, they don't pin down inflammation as its cause.
Lupus patients exhibit signs of heart disease
There's a story in this picture, as there is in each one and in the group as a whole, but because of Baran's ambiguous position both inside the story and out, at an angle to the image and yet facing it straight on, it's partly a story about not being able to pin down just what the story really is.
TRACEY BARAN
Further studies with the Sloan data may help pin down the physical traits of the still-elusive dark energy, Frieman notes.
Strengthening the case for dark energy. (Repulsive Astronomy)
Rich in description and allusions (history, geography, rock bands), Chang's demented dialogue was also highly structured, in almost musical fashion, with constant repetitions and variations - making the language as difficult to pin down as the elusive Chang himself.
JOHN HAGAN ON John Jesurun
"When the number of errors is guaranteed to be small, and one puts in sufficiently large amounts of redundancy in encoding one's transmission, then it is possible to pin down the transmitted message," Sudan says.
Guessing secrets: applying mathematics to the efficient delivery of Internet content
." The visual images - an angry man encased in tubes, a two-headed, masked figure, an 18th-century dandy, among others - were also difficult to pin down. A modern-day Pandora's box, this piece let loose an endless stream of ruminations on the corporeal, on our uneasy place in this world, and on the difficulty of describing it.
Judith Barry: Gallery Xavier Hufkens
The author emerges in this image--as he does throughout the pages of his pseudo-autobiography, Roland Barthes by Roland Barthes--as riven, distant, hard to pin down: he is at once effeminate and boyish, graceful and gawky, a little man and a childish sissy.
A clown's coat
Archaeologists have for decades tried to pin down when the first farming communities appeared in Europe and how farmers spread across the continent to replace mobile groups of hunter-gatherers.
Farmers took fast track in settling Europe
Thwarted in my attempts to pin down, to explain Perlman's proceedings, I realized that one cannot grasp that slippery thing called art.
Hirsch Perlman
The connection between lupus and the nervous system has been difficult to pin down because patients don't link subtle cognitive problems to the disease, he says.
Protein may key lupus' attack on neurons. (Science News of the week)
Researchers have yet to pin down paternity lines for chimps in eastern Africa, counters anthropologist William C.
Female chimps don't stray in mate search
Because each of the young stellar groups is a different age, astronomers hope that by examining several, they can pin down the time line for the series of events necessary for planet formation.
Captured on Camera: Are They Planets?
From that calculation, they can pin down a value for the Hubble constant, a measure of how rapidly the universe is expanding.
Variable quasar may help measure the cosmos