Ignore, dub, to not answer.

In the vBulliten software, there's a reputation system that increments and decrements depending on the type of reputation received. Users will either give or take away points by approving or disapproving with a post's content. Green bars represent a positive reputation while Red represents a negative reputation.

negging or getting negged occurs when a user takes away reputation points from another user. Often happens when users shitpost/troll/etc.

A statement or action that briefly disqualifies oneself from being considered a potential suitor. Used by pickup artists on beautiful women to relieve fears of being hit on uncomfortably.

Negative compliment that throws a pretty woman off their game

(n.) shortened form of "negative", meaning not in the affirmative, in the converse, detrimental, or unfavorable.

negged (adv.) past-tense of neg, to have denied, refused, dismissed, shot down, et al.

To show displeasure with orgasm like qualities

It's a way to pick up girls. How it works is you use remarks to tap into female insecurity; Shake their confidence.
Neg is a negative remark wrapped in a back-handed compliment.
So your neg will confuse and intrigue them and maybe even shake their confidence a little bit, but only enough for them to fall from the clouds and be interested in talking to you. Its way to get threw their defenses at bars and such.