What it means
A lab rat is the person who gets thrown in first to try some new thing out, so everyone else can stand back and watch the chaos unfold. Could be a trial, a beta app, a new system at work, or some dodgy drink your mate swears is fine. They're the one finding out the hard way whether it's decent or a full-on disaster.
Usage examples
"I signed up to be a lab rat for the sleep study, three nights wired up to machines for a bit of cash."
"The marketing team needed lab rats for the new mobile app, I volunteered, got the beta version on my phone for two weeks, and reported sixteen bugs before the official launch."
"Mum has been a lab rat for every new diet on the market since the nineties, started Atkins in 2003, did keto last winter, and now refuses to talk about food at family dinners."
"They rolled out the new booking system to our team first, so we were basically the lab rats while the rest of the office sat there pretending not to watch."
"I'm not being your lab rat for that mystery energy drink, mate. You have a sip first and let your organs file the review."
Where it comes from
It comes straight from actual laboratory rats used in scientific testing and experiments through the 20th century. From there, English stretched it into everyday slang for any person used as the first tester for something new, risky, or not fully trusted yet. The image stuck because it instantly screams unwanted experiment energy.
Other ways to say it
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