斗嘴 is a separable verb (离合词) meaning to argue verbally or to have a back-and-forth verbal exchange, ranging from serious squabbling to light-hearted banter. Because it's separable, you can insert time expressions, measure words, or other elements between 斗 and 嘴, like 斗了半天嘴 ('squabbled for a while') or 斗过几次嘴 ('had a few verbal spats'). It's commonly used between family members, friends, or colleagues to describe playful or mild arguments.