In an episode of the big bang theory, someone says "Take a jacket, it's shpritzing a little." Is shpritzing are real word? What does it mean?
This is a real word. It's generally spelled spritz, even though it is commonly pronounced shprits. What it means in this context is not raining but raining lightly, or in non-Yiddish-influenced English, drizzling.
The word spritz came from Yiddish or German; in German spritzen means to squirt. In Yiddish the corresponding word is shpritsn (שפּריצן). It was originally pronounced with an sh: shpritz, because that's the way it's pronounced in German and Yiddish. It still commonly is pronounced that way.
I know this word as spritz (in terms of spelling), and /sprɪts/ (in terms of pronunciation). The dictionary gives both pronunciations (with and without sh):
spritzed; spritzing; spritzes
Definition of spritz
: to disperse or apply a spray
/ sprɪts, ʃprɪts /
verb (used with object)
1 to spray briefly and quickly; squirt:
He spritzed a little soda in his drink.
I see original as somewhat unusual, but understandable. Given the context, I take it to mean that it's raining. Again, this is unusual to me, but possible, as a kind of improvisation, or "creative" utterance. Maybe it has greater currency among other speakers.