It describes a situation which has a fancy climax but with a simple ending. For example, if an author spend a whole page writing how he/she struggled to catch the fish and say in the end, "then I let the fish go," them it is anticlimactic.

something that causes disapointment

the opposite of building to a climax. instead, making potentially rising ideas and energy steady, or falling.

relating to a person's tone of voice; sounding dull, less enthusiastic, or normal tone in cases of excitement.

A dull or disappointing ending or result.

Series of events having unimpressive ending

Totally a word.

Also a dinosaur.