It's a bit like asking "how does one word 'dance'?" Words themselves don't engage in physical actions.
Possible interpretations:
* Metaphorical usage: You could use "scrimmage" metaphorically to describe a verbal battle or intellectual clash: "Their arguments were a verbal scrimmage, each trying to outmaneuver the other."
* Wordplay: "Scrimmage" might be used in a playful or nonsensical way, like a riddle or a pun.
To answer your question more directly, words don't "scrimmage" in a literal sense. They exist as concepts and are used to communicate ideas.