A trip code is a code used in anonymous threads like 4chan to determine whether or not the anonymous poster is authentic or not.
It assigns a code to the end of your name.
When you add the pound (#) symbol to the end of your name followed by a word, like a password that only you know, it scrambles the word into a code. That way it's undetectable and can be used over and over again.
On AnonIB, using the trip code "#banana" translates to the code shown to Anons as "!5RRtZawAKg".