zone out

Related to zone out: space out

zone out

1. To lose focus or stop paying attention to something, usually unintentionally. The term can be used to indicate that someone has focused on one thing to the exclusion of everything else. I think I must have zoned out during that lecture, because when it was over I realized I didn't remember anything the professor said. Jerry kind of zones out when he plays video games, so you have to be really loud to get his attention.
2. To intentionally ignore or block out certain stimuli, distractions, etc. In this usage, a noun or pronoun can be used between "zone" and "out." When you're playing, you have to zone out everything except what's happening on the field. I know Aunt Lula can be aggravating, but she's only here for a few days, so just try to zone her out.
See also: out, zone
Farlex Dictionary of Idioms.

zone out

Stop paying attention, dissociate oneself from a situation. Also, engage in a mindless activity. For example, When Felicia starts talking about her ailments and her friends' ailments, I totally zone out . This idiom also occurs in the passive, be zoned out. It originally alluded to narcotic intoxication and then was broadened to other kinds of dissociation. For a near synonym, see tune out, def. 2. [Slang; second half of 1900s]
See also: out, zone
The American Heritage® Dictionary of Idioms by Christine Ammer.

zone out

v. Slang
1. To lose concentration or become inattentive: I sensed the class was zoning out, so I started talking louder.
2. To lose awareness of one's surroundings: An hour after I took the cough syrup, I lay back in bed and zoned out.
3. To refuse to pay attention to someone or something; ignore someone or something: The athlete zoned out the jeering crowd and made the free-throw shot. Every time I try to give you advice, you zone out everything I say.
4. To cause someone or something to lose awareness of one's surroundings: The medication that I take zones me out.
5. To exclude someone or something by restricting a section of an area or territory: Farmers complain that the government has zoned them out of the best farmland. The city zoned out adult entertainment companies.
See also: out, zone
The American Heritage® Dictionary of Phrasal Verbs.

zoned (out)

1. mod. alcohol or drug intoxicated. What’s the matter with your eyes? Get a little zoned last night?
2. mod. exhausted. After a day like this, I’m really zoned.
See also: out, zone
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • bump (up) against (someone or something)
  • bump against
  • bump into
  • bump into (someone or something)
  • find (oneself) without (someone or something)
  • find oneself without
  • have an accident
  • knock someone out
  • knocked out
  • knockout