What is the meaning of Backhanded?

With the back of the hand.

Involving a backward flip of the hand.

Insincere, sarcastic, ironic, or self-contradictory.

Indirect.

Backwards, turned around.

inclining to the left

Retrospective, occurring after the fact rather than in advance.

Self-serving, corrupt, slipshod, or neglectful.

simple past and past participle of backhand

In a backhanded manner.

Source: wiktionary.org