What does "whatcha" mean?

Contraction of what + are + you.

What is a synonym for "whatcha"?

Common synonyms include: wotcher.

/ˈwʌt͡ʃə/ contraction, slang

contraction, slang ·Moderate ·College level

Contraction

1
Contraction of what + are + you. abbreviation, alt-of, colloquial, contraction
"Whatcha doin'?"
2
Contraction of what + have + you. abbreviation, alt-of, colloquial, contraction
"Whatcha been up to?"
3
Contraction of what + do + you. abbreviation, alt-of, colloquial, contraction
"Whatcha think?"
4
Contraction of what + you. abbreviation, alt-of, colloquial, contraction
"Do whatcha gotta do!"

""Your Majesty, Ganon and his minions are not in the house!" "Whatcha talkin' 'bout?""

From what + -cha.