bullir

To boil or bubble (literally, of a liquid) and, very commonly, to bustle, swarm, or teem figuratively (la plaza bullía de gente, "the square was teeming with people"). Irregular like gruñir/bruñir: the stem-final ll absorbs a following unstressed i, so it's bullendo and bulló, not bulliendo/bullió.

• El agua bullía en la olla. — The water was boiling in the pot.
• El mercado bullía de vendedores y compradores. — The market was teeming with sellers and buyers.
• Las ideas bullían en su cabeza sin parar. — Ideas were swirling nonstop in his head.

Learners often write bulliendo/bullió by regularizing the ending — the i after ll disappears, giving bullendo (gerund) and bulló (third person preterite), the same pattern as bruñir/gruñir.

• expression "Bullirle/hervirle la sangre" — A fixed expression meaning to be furious or seething with anger — the more common variant uses hervir (to boil), but bullir la sangre appears as a recognized, if less frequent, alternative in Spanish dictionaries and usage.