A sneaking hunch.
A sneaking manner.
A sneaking fondness for candy.
A sneaking suspicion.
Now I know why you came sneaking out here.
It was Shipton sneaking in.
"Lydia, I don't like this sneaking around business," Dean said.
There was no sneaking in with a butler and maid waiting at the door.
Sneaking into their bedroom, she grabbed some clothes and then dressed in the kitchen.