(noun) The practice of secretly showing one or both testicles while standing in the background of a photo. Can be either the through-zipper or above-trousers type.
Made famous by Nathan in the Chris Lilley comedy Angry Boys.
Nath's got this new thing he does, it's called sneaky nuts. Fucking classic. Stands in the back of a photo, rips out one ball, sometimes two. Sometimes through the zipper, other times above the trousers. He tends to mix it up a bit so you never know what you're gonna get. Fucking brilliant Nathan is.