To sidle means to walk in a shy or sneaky way, especially when you don't want to be noticed.
Sidle can make people think of being sneaky or trying to hide.
Examples:
She tried to sidle past the teacher without being seen.
The cat will sidle up to you when it wants food.
He likes to sidle around the room and surprise people.
The mouse tried to sidle into the kitchen without being caught.
The ninja can sidle up to the bad guys without them knowing.
I sidle up to my friend and say 'Boo!'