Puerto Rican slang (and also used in some other Caribbean islands). Usually, it means to be head over heels in love. It can also be used as to describe someone who is very excited about something. In Mexico and Central America, it means to be very pleased about something.
(culeco is masculine, culeca is feminine)

lil mad is like big mad but the opposite, you mad but not mad to the extent of pullin somthin

A fat ass