An act in which an assailant acquires a small amount of 'smeg' (usually their own) and rolls it between the finger and thumb. Once the smeg is even distributed they nip the septum (the bit between your nostrils) of the victim thereby depositing the cheesy smell in a vary porous skin area which doesn't leave for days. Nor does the area lend itself vigorous washing.
Steve landed an awesome cheesy nip on Jimbo the other day. Fu*king gross man as you just know that Steve doesn't wash his tackle for days at a time.