This is one of my favorite online resources for technical Behavior terms: Glossary of Terms for the Experimental Analysis of Behavior.
It is hosted by the University of Iowa and was written by: Brittan Barker, Joy Kreider, Jessie Peissig, Greta Sokoloff, Maura Stansfield.
I’ve used this glossary for about 5 years now when I need a definition. It’s easy to navigate and simple to understand using language that seems just a little bit less mumbo-jumbo-ish than many of the other resources that I’ve ran across on the net.
Feel free to add your favorite resource in comments below.