A spear-thrower, spear-throwing lever or atlatl is a tool that uses leverage to achieve greater velocity in dart or javelin-throwing, and includes a bearing surface which allows the user to store energy during the throw.

What is an Atlat?

: a device for throwing a spear or dart that consists of a rod or board with a projection (such as a hook) at the rear end to hold the weapon in place until released.

What is meant by javelin throw?

The Javelin throw is a track and field event where the javelin, a spear about 2.5 m (8 ft 2 in) in length, is thrown. The javelin thrower gains momentum by running within a predetermined area. Javelin throwing is an event of both the men's decathlon and the women's heptathlon.