In a way that is like a shadow, or in a way that is not clear or easy to see.
The word shadowily can make people think of mystery, darkness, or something hidden.
Examples:
The figure moved shadowily through the dark alley.
She disappeared shadowily into the fog.
The cat crept shadowily along the wall.
The ghostly figure danced shadowily in the moonlight.
The treasure was hidden shadowily in the cave.
The ninja moved shadowily, unseen by anyone.