I've heard the expression before, but always applied to inanimate objects and used to mean the same thing as "pooched", "wasted", or my old favorite, "chootched".  Actually the word "pantsed" was first coined in the 1980's and refers to one being humiliated by having one's pants pulled down by a third party in public...

I am grateful to say, this is one thing that the kids who picked on me mercilessly in school never tried.  I think they would have thought it "too gay" or something.

But it's a pretty funny word, pants, and has been used to mean various things.  Apparently in Australia, it can mean "luck".  If someone manages to pull off something improbable by sheer luck, it is appropriate to say "Pants!"

It can also mean crappy or lousy as in "I just checked out that House of the Dead movie, ugh, that flick was pants."

Also it can mean nonproductive activity... as in "just pantsing around".

"Baggy-pantsing" is a hacker term.  When one hacker exposes another for leaving his computer insecure, the exposed hacker has been "baggy-pantsed".

In researching the various uses of the words pants and pantsed, the weirdest thing I found was this guy's site on zutroy.com.  Apparently he has a fetish for Star Wars and pants...

...Vader: "I am altering the pants. Pray I don't alter them further!"

Vader: "I find your lack of pants disturbing."

Luke: "What's in there?"
Yoda: "Only that which you take with you. Your pants - you will not need them."

vader: "Pants do not concern me, Admiral."

Leia: "You came in those pants? You're braver than I thought."

Han: "The pants may not look like much, kid, but they've got it where it counts."

Admiral: "These pants contain the ultimate power in the Universe. I suggest we use them."

Lando: "Han will have those pants down. We've got to give him more time!"

Vader: "General Veers, prepare your pants for a surface attack."

Officer: "TK-421. . . Why aren't you in your pants?"

Vader: "You are unwise to lower your pants."

Vader: "She must have hidden the plans in her pants. Send a detachment down to retrieve them. See to it personally Commander."

Lando: "That blast came from those pants. That thing's operational!" ...

Weird. Funny, but weird. 

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