It has no use in my vocabulary especially within the fitness and health field. However it is often used as a lamens term to replace contract. Depending on the client or patient, one might conceptualize, visualize or execute differently depending on the word used. Therefore, I believe as long as you maintain a constant vocabulary you should be beneficial in translating your point to the client or patient.
Fuel the movement,
I agree that in our professional vocabulary, or in a situation where I’m trying to teach my client the correct terminology I would not use the word squeeze. But, I also believe in using whatever words, visualization or analogy that will help the client (particularly a beginner) understand the feeling or the concept that I’m trying to relay. So, with that being said, I’m not too terribly bothered by whatever method helps the client relate to what you’re trying to convey – as long as you also give them the correct concept or term at some later point. Educating the client makes for a healthier client in the long-run.
If contract isn’t reaching clients, try “tighten” (used in dance for gluts) or “hollow-out/scoop” (used in Pilates, C-sit for abs). I agree with the other comments, start with the correct term and then supplement with visual/linguistic cues; the client will know the difference and appreciate having many ideas at their disposal.
I worked with pregnant clients and love this trick for kegels: When driving and you are waiting at a stop light, visualize your pelvic floor rising and lowering like an elevator (5 counts up/exhale, 5 counts down/inhale). It worked the exercise into their already busy days and stayed with them after delivery during post-partum rehab.