A distinct type of palm-heel strike which is physically distinguishable by striking in a forward direction - with fingers pointing downward.

Comments:

This strike is most typically effected on a relatively horizontal line. Because of orientation of this strike, it is often completed without the standard clawing conclusion.

If the strike were to follow a slightly more circular line of travel, the usual clawing portion would then be a more viable option.

Typically, this strike employs a Thrusting (or Snapping) Method of Execution; but can also use:

Lift

Loop

Scoop

Due to the nature of this strike's application, the clawing portion is always excluded on the Snapping version - and often on the Thrusting (or other) versions.

The word underhand, in this case, refers to the direction of the fingers (pointing downward), forcing the palm to point upward (i.e. underhanded).

This strike typically follows a Line of Travel that is relatively parallel to the vertical (width) center-line (and relatively perpendicular to the vertical (depth) center-line).

The term underhand, in this context, is general in nature mostly refers to the orientation of the hand, not the path of the strike (either linear or circular).