Indicator:

1.a dial gauge used on the rig to measure the hookload.

2.

Substances in acid-base that, in solution, change color or become colorless as the hydrogen ion concentration reaches a definite value, these values varying with the indicator.

In other titrations, such as chloride, hardness, and other determinations, these substances change color at the end of the reaction.

Common indicators are phenolphthalein, and potassium chromate.