Cecil uses this word in one of his columns [about states of matter] but my dictionary only lists the bird.
Karen Lingel, who is a both penguinist plus a regular poster on the alt.fan.cecil-adams USENET group, notes that A penguinist is a particle physicist who studies one-loop decays of B mesons, whimsically called “penguin” decays on her web page at: http://w4.lns.cornell.edu/~kll/
Karen is also an official staff member on the Straight Dope Science Advisory Board… check out her latest: What is antimatter? … where she also (way down in the text) mentions the job of penguinist.
wow - mind-expanding!! (I know, I know - if you start small it doesn’t take much…)
thank you Straight Dope - this is the type of thing I show my beloved when she asks why I spend so much time at this site.
Yes, wow. I can amaze my friends. 'Hey stop being such a penguinist!"
A penguinist is someone who’s an expert with the Linux operating system. 
“I had a feeling that in Hell there would be mushrooms.” -The Secret of Monkey Island
Sorry. I’ve been calling myself a penguinist for so long, it’s become part of my identity. It’s sort of an inside particle physics joke – like calling yourself a Star Warsist or something.
-k-
First of all, I’m frothing with curiosity to
read Cecil’s column mentioning such a
delightful word…could we please get a
link?
And secondly, this just absolutely begs the
question: Why are “one-loop decays of B
mesons” called “penguin” decays, whimsically
or not? Was it the namer’s favorite bird or
something? When they make that one loop, do
they outline the shape of a penguin?
Kara’s Bizarre Movie Quote for the Day:
“Such as who we are, what we’re doing…” “…and why I have a picture of a burger on the wall.”
Physicists; pub; dart game; loser has to get the word “penguin” into Physical Review D. The loser, theorist John Ellis, was working on one-loop decays at the time.
Now: Physical Review has an explicit rule about introducing new jargon as a joke.
Sometimes people try to draw one-loop decays that look like penguins. They don’t look all that compelling – either as penguins or as one-loop decays