My T tends not to use a lot of them, but all it takes is for me to ask if I don't understand, and he will explain what he means. These are terms he has used and explained to me:

EMDR (that one took a lot of explanation!)
Trauma
Ego states
Gestalt dreamwork
Negative cognition
Positive cognition
Narcissist Personality Disorder
Healing Circle

Sometimes I don't want to ask him what the word means, so I don't. Sometimes I know but don't really know what it means. Like he says I "dissociate" sometimes. I don't really know what that means, never had it explained to me, but I kind of do know. But I don't want him to explain it to me. Does that make sense? Sometimes I prefer not to get the "official explanation." One time recently he used the phrase "mentally ill" and I don't know what he means by that either, as he has never used it before. I am ready for definitions when I am willing to ask.

Riptide, if your T uses words that confuse you, could you ask him to explain?