foot fault n. in jurisprudence, a minor criminal or procedural violation; a legal misstep. Etymological Note: This is a direct borrowing from net-based sports, such as tennis, badminton, and volleyball, where a foot fault is the placement of a foot outside the baseline when serving. (source: Double-Tongued Dictionary)
Further reading
Understanding the varieties of conversational styles can mean the difference between feeling you’re understood and being insulted. “High-involvement” speakers interrupt or talk along with someone else to signal their enthusiasm...