not at all

WordReference Random House Learner's Dictionary of American English © 2025

not /nɑt/   adv. 

1. (used with verbs like[be, have,] and[do,] and with modal verbs, to express the opposite of the main verb, and also to express denial, refusal, prohibiting, etc.:
   I do not remember the answer. You must not think about it. It's not far from here. They are not coming.
2. (used with verbs like[think, want, seem, appear, expect,] and others that have another verb in a phrase or clause following, to express the opposite of the verb that follows):
   He did not seem to be ready (= It did not seem that he was ready). He did not want to go (= He wanted not to go.) I did not expect to see you here (= I expected that I wouldn't see you here).
3. (used before a singular count noun) not even one (expressing emphasis about the lack of something):
   [~ + a/one + noun] He had not a penny to his name. Not a single missile got through the defense system. Not one student could name the president.

Idioms

4. not at all:
   • (used as an answer to someone else's thanks):
     "I appreciate your help.'' —"Not at all.''
   • (used to emphasize an answer of "no''):
     "Did you like the show?'' —"Not at all!''

WordReference Random House Unabridged Dictionary of American English © 2025

not  (not), adv. 

1. (used to express negation, denial, refusal, or prohibition):
   You must not do that. It's not far from here.
2. Slang Terms U.S. Slang. (used jocularly as a postpositive interjection to indicate that a previous statement is untrue):
   That's a lovely dress. Not!

• 1275–1325; Middle English; weak variant of nought

not-, 

1. var. of noto- before a vowel.

NOT  (not), n. 

1. Computing a Boolean operator that returns a positive result if its operand is negative and a negative result if its operand is positive.