To look under a girl's shirt or panties for the "goods"
Guy 1: Bro, she's hot!
Guy 2: Damn, did you get a look under the hood?
Guy 1: Hell ya I did, looks like she got her engine steamed.
The best of the best.
"Wow your homemade pot roast is cream under the hood!"
See also; The bee's knees, the dog's bollocks
Wow this club is cream under the hood!