When you and your families/roomates/girlfriends tooth brush are all in the same cup for holding when not in use and the bristles of your brush are touching the bristles of there brush and therefore the toothbrushes are kissing.

Generally a bad thing because the persons plaque is now shared with your plaque. IT is not a bad thing however when it is with a hot girl.

Internet persona(s) who happens to follow you and you happen to follow them back and maintain communication with and have a mutual liking for eachother whether it be friendship wise, etc. (Mutuals if more than one mutual)