nap

II. nap² BrE AmE verb (past tense and past participle napped, present participle napping) [intransitive]
[Language: Old English; Origin: hnappian]
1. be caught napping informal to not be ready to deal with something when it happens, although you should be ready for it:
The German team were caught napping and Lampard scored the winning goal.
2. to sleep for a short time during the day

Oxford Advanced Learner's Dictionary

verb (-pp-) intransitive
to sleep for a short time, especially during the day
• I tried to nap on the plane.
see catch sb napping at catch
Verb forms:

Word Origin:
n. sense 1 and v. Old English hnappian Germanic
n. sense 2 late Middle English noppe Middle Dutch Middle Low German noppe ‘nap’ noppen ‘trim the nap from’
n. sense 3 early 19th cent. napoleon

Example Bank:
• During the flight you are advised to nap if possible.
• Studies show that napping at work can help keep you alert and refreshed.

• Try not to nap during the day.

Cambridge Advanced Learner's Dictionary

Cambridge Advanced Learner's Dictionary - 4th Edition

nap / næp / verb [ I ] ( -pp- )

to sleep for a short time, especially during the day:

He likes to nap for an hour when he gets home from work.

Collins Advanced Learner’s English Dictionary

nap

[næ_p]
naps, napping, napped
1) N-COUNT If you have a nap, you have a short sleep, usually during the day.
  Use your lunch hour to have a nap in your chair...
  I might take a little nap.
  Syn:
  snooze
2) VERB If you nap, you sleep for a short period of time, usually during the day.
  An elderly person may nap during the day and then sleep only five hours a night.
  Syn:
  doze
3) N-SING The nap of a carpet or of a cloth such as velvet is the top layer of short threads, which usually lie smoothly in one direction.
4) PHRASE: V inflects If someone is caught napping, something happens when they are not prepared for it, although they should have been. [INFORMAL]
  The security services were clearly caught napping.

Merriam-Webster's Advanced Learner's Dictionary

²nap verb naps; napped; nap·ping [no obj]
1 : to sleep for a short period of time especially during the day
• He's napping [=dozing] on the couch.
2 : to be in a state in which you are not prepared to deal with something because you were not paying attention
• The goalie had to be napping when that ball got by him.
• When the problem appeared again, the government was caught napping. [=the government was not prepared to deal with it]