rumián

In a sentence

• Los caballos rumiaban tranquilamente en el establo.

  The horses were chewing calmly in the stable.

  Here, 'rumiar' indicates the act of chewing food repeatedly, as it often happens with herbivorous animals.

• Rumiaré las ideas antes de tomar una decisión final.

  I will mull over the ideas before making a final decision.

  The usage of 'rumiar' in this sentence is metaphorical, signifying thinking deeply or mulling over thoughts or ideas.

• Le sugerí que no rumiara tanto sobre el pasado.

  I suggested him/her to not dwell so much on the past.

  This sentence uses 'rumiar' in an emotional or psychological sense, to mean dwelling on or revisiting certain thoughts repeatedly.