Consummate means complete, finished, or masterful. If you refer to someone as a consummate chef, then you are saying he is the ultimate chef. If you say someone is a consummate jerk, then you are saying he is the ultimate jerk.
Consummate can be used to describe something good or bad: consummate joy, a consummate liar. To consummate means to bring something to completion, but it often refers specifically to making a marriage complete by having sexual relations. The adjective is pronounced KÄN-sə-mit, but the verb is pronounced KÄN-sə-māt.