a snap

snap

1. verb To go crazy. One day, she just snapped and started threatening people in the office.
2. noun Something that is very easy or effortless to do. A song like this will be a snap once you get more comfortable with playing the guitar.
3. A snapshot photograph. Oh, those snaps won't work—they're too dark.
Farlex Dictionary of Idioms.

a snap

verb
See snap
See also: snap
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • high
  • high, wide, and handsome
  • wear (one's) apron high
  • bummer
  • angle
  • angling
  • fire and brimstone
  • mickey mouse
  • rear end
  • garbage
References in classic literature
“A snap, a snap!” shouted the negro, springing from his crouching posture like a madman, before his bird.
It’s contrary to the reason of the thing, boy, that a snap should count for a fire, when one is nothing more than a fire-stone striking a steel pan, and the other is sudden death; so get out of my way, boy, and let me show Billy Kirby how to shoot a Christmas turkey.”
Now, in duels, where both parties shoot, it is generally the rule that a snap is a fire; and if such is the rule where the party has a right to fire back again, it seems to me unreasonable to say that a man may stand snapping at a defenceless turkey all day.
Then he fought, his teeth flashing in a snap that sank them into the hand.
Her hand went out gingerly, and the growl rose in volume and key till it culminated in a snap.
So he made a snap at the shadow in the water, but as he opened his mouth the piece of meat fell out, dropped into the water and was never seen more.