One of one's parents. (Often used in the plural to indicate both parents.) Which parental unit is coming to pick you up from school today, nerd? I'd love to come, but I need to check with the parental units if it's all right.

slang One's parents. I'll have to check with my parentals if I can borrow the car for the evening. A: "Hopefully the parentals will be asleep by the time we get back." B: "Don't call them your parentals, dude. You sound like a dweeb."