whenever they get together; every time they meet
Fixed expression meaning that two or more people always do something (often something troublesome or gossipy) whenever they meet. Often used with verbs like 喧嘩する, 話し込む, or 悪口を言う.
Those two fight every time they get together.
Whenever they meet, they gossip about someone.
A set phrase combining the verbs 寄る (to drop by, to gather) and 触る (to touch), literally 'when they gather and touch,' implying close contact leads to certain repeated actions.