The meeting overheated as the argument became too intense.

overheated 是动词 overheat 的过去式。overheat 由前缀 over-（表示"过度"）和动词 heat（加热）组成，字面意思是"过度加热"。在这里用作比喻义，表示"（气氛）变得过于激烈/紧张"。