Furtive is not a noun.
The man across the aisle in the bus shot me a furtiveglance.
In this sentence furtive is an adjective.
furtive means sneaky
The records showed furtive criminal activity.
There is no common prefix for furtive.
FURTIVE (?) - hidden, secret, sneaky, covert, clandestine
clandestineAdjectiveFormal secret and concealed: a base for clandestine activities dictionary.com
Its a kind of sideways way of looking at anything for a very short period of time.Quick look
The records showed furtive criminal activity.
There is no common prefix for furtive.
His furtive movements made it hard for them to catch him.
Example sentence - Her furtiveness backfired on her.
They made furtive plans in the hopes of surprising him on his birthday.
He looked over his shoulder in a furtive way. (In other words as an adjective.)
A glance that is sneaky and secretive.Sentence: The robber gave a furtive glance to the police.
The thief looked about in a furtive manner just before picking my pocket.
The convict made many furtive attempts to escape from prison.
She cast a furtive glance over her shoulder, then unlocked the door and entered the house.
Assertive
His actions were secretive and furtive, as though he were planning to break a law.