The act of perching on the sill of a lover's window in order to spend time in said lover's dorm without breaking the school code. Windowsilling dates offer, but are not limited to, fine dining, cuddling, movie watching, lip-to-lip touching and sleeping.
This art is commonly used by students at Liberty University attempting to maintain the Liberty Way.
Yo, check it out, Kathy is totally windowsilling over on the hill right now.