(Via Boing Boing)
From Webster’s 1913 Dictionary:
Ba′thos (bā′thŏs), n. [Gr.βάθοσ depth, fr.βαθύσ deep.] (Rhet.)
A ludicrous descent from the elevated to the low, in writing or speech; anticlimax.
Bathetic is producing an unintentional effect of anticlimax: the movie manages to be poignant without becoming bathetic.