Negation symbol, in logic (5)
I believe the answer is:
tilde
'negation symbol in logic' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tilde that I've seen before include "Style detail" , "Accent (used over n) in Spanish and Portuguese" , "Significant mark" , "Mark placed over N in Spanish" , "Mark, sometimes on keyboards" .)