( a combination of the words silly and behaving), this phrase is said of small children who are not misbehaving morally or otherwise, but are nonetheless engaged in an activity that is considered silly by adults.
a boy comes home, takes his pet hamster out out of its cage, and brings him out into the backyard, and puts said hamster on the grass in the yard. The hamster starts running away.

The boy's mother starts yelling : Peter you silla-having troglodithe, what are you doing, you silly? bring Jerkins (the hamster) back in immediately, or he'll just get lost. Besides, i need to feed him.

Peter: okay, hang on mom, let me go find Jerkins.
by Sexydimma September 3, 2012
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