sandbag /(?)/

sand·bag

sandbag

A bag filled with sand; small sandbags may be used as a weapon, or larger ones to build walls or as ballast; as, they kept the flooding river from the area by buiding a temmporary dike out of sandbags.

To treat harshly or unfairly.
To hit something or somebody with or as if with a sandbag.
To protect or strengthen with sandbags; stop up; as, the residents sandbagged the beach front.
To thwart (another person's plans) by surreptitious maneuvers; as, he sandbagged my proposal by talking in private with other members of the committee. [informal]
To intimidate or coerce, especially by crude methods. [Informal]
To deceive and take advantage of (a person) by misrepresenting one's true intentions. [Informal]
To encourage opponents into betting more by first refraining from betting while having a strong hand, and only later raising the stakes. In informal games, certain types of sandbagging are forbidden. (Poker)