noun
preachy priest; tub-thumping preacher; pulpiteer
Derogatory term for a Buddhist priest or preacher who is overly fond of lecturing or moralizing, often with a condescending tone. The word 坊主 (ぼうず) itself can be mildly derogatory when referring to a priest.
あの説教坊主の話はいつも長くて説教くさい。
That preachy priest's talks are always long and preachy.
彼は説教坊主みたいに人の欠点を指摘する。
He points out people's faults like a pulpiteer.
Compound of 説教 (せっきょう, 'sermon, preaching') and 坊主 (ぼうず, 'Buddhist priest'). The derogatory nuance comes from the combination of the critical view of excessive preaching and the sometimes pejorative use of 坊主.