A Chipmunk is a sexual act by definition that includes both the dick and balls in the partners mouth at the same time. The male then busts his nut and hibernates for winter.
Lee:What did you get into last night?
Kevin:What do you mean what did I get into? What didn't I get into is a better question cus I went straight chipmunk on her ass last night.
Lee:Oh word
When a woman is able to fit a man's penis and testicles into her mouth simultaneously while performing oral sex, much in the same way that a chipmunk can shove copious amounts of nuts into its mouth while eating.
A child conceived through clandestine means on the female's part. Said means usually consist of the female giving fellatio, pretending to swallow, concealing semen in the side of her mouth (as a chipmunk), and later transferring the semen from the mouth to the vagina.
"... but Steve told me last year that they didn't want to have kids! I bet that sneaky bitch Jill made herself a chipmunk baby."