(idiomatic) not exactly but slightly

(mathematics, logic) An operation on logical values that changes true to false, and false to true.

(idiomatic) Worth nothing or next to nothing.

(emphatic) Not in the least.

plural of notum

(idiomatic) (It's of) minor importance, at least not as important as it first seemed.

(informal) Ellipsis of I'm afraid not.

Any indication similar in nature to nota bene. / Something deserving of close attention or of careful notice.

And not.

Negates the meaning of the modified verb. / To no degree. / (understatement, litotes) Used to indicate the opposite or near opposite, often in a form of understatement.