underhand

Short definition from Wiktionary

Adjective

1. 1
   Secret; clandestine.
2. 2
   Dishonest and sneaky; done in a secret or sly manner.
3. 3
   Thrown (etc.) with the hand brought forward and up from below.

Adverb

1. 1
   With an underhand movement.
2. 2
   In a sly, sneaky or secret manner.

Verb

1. 1
   To toss or lob with an underhand movement.
2. 2
   To trick, deceive or gull.
3. 3
   To excavate downward in successive steps or horizontal slices while positioned above on unbroken ore.

Noun

1. 1
   The lower of two hands, the hand under the work.