The act of being extremely anal. Insisting things be done a certain way. Freaking out when things are done in a way you don't approve of. Can be used as a character trait rather than referring to someone with the disease. Can cause feelings of anxiety. Also can be a verb.
Color-coding your sock drawer according to the spectrum of the naturally occuring colors in the rainbow sequence. Not allowing other members of your household to arrange things because they will 'mess it up'. 'Someone keeps putting my coffee cup on the left side of the cabinet shelf instead of the right side!!! You're making my OCD twitch!' 'Don't OCD on me!'