Forelock \Fore"lock`\, n.

1. The lock of hair that grows from the forepart of the head.

2. (Mech.) A cotter or split pin, as in a slot in a bolt, to prevent retraction; a linchpin; a pin fastening the cap-square of a gun.

Forelock bolt, a bolt retained by a key, gib, or cotter passing through a slot.

Forelock hook (Rope Making), a winch or whirl by which a bunch of three yarns is twisted into a standard. --Knight.

To take time, or occasion, by the forelock, to make prompt use of anything; not to let slip an opportunity.

Time is painted with a lock before and bald behind, signifying thereby that we must take time by the forelock; for when it is once past, there is no recalling it. --Swift.

On occasion's forelock watchful wait. --Milton.

Source: Webster's Revised Unabridged Dictionary (1913)