To portray the meaning of something.
I define the length of that cock as 2 feet.
ayon kay Matteo ika-12 ng Setyembre, 2003
To give a definition for a word, phrase, acronym, or abbrevation.
"I am defined as: "Above all others"
ayon kay Ravek ika-20 ng Marso, 2004
to give a meaning to a word.
How would I define an apple?
ayon kay Anonymous ika-09 ng Setyembre, 2003