"until you were at least pinned or engaged"
Phi Mu fraternity pin
Creative Commons AttributionPhi Mu fraternity pin - Credit: Phi Mu Fraternity

'Pinning' is a college fraternity member's way of showing commitment to a relationship with his girlfriend by giving her his fraternity pin (sometimes known as 'a pledge pin' or 'new member pin'). Generally, pinning is seen as the equivalent of an engagement.

It is closely related to the concept of 'lavaliering' which involves a fraternity member giving his girlfriend a 'lavaliere' or necklace which includes the fraternity's letters in its make-up.

Generally, lavaliering precedes pinning.