noun.
An optical instrument for the precise measurement of very small time intervals.
The Century Dictionary and Cyclopedia
noun.
An instrument for measuring extremely short intervals of time. Specifically
noun.
An instrument for measuring the velocity of projectiles.
the GNU version of the Collaborative International Dictionary of English
noun.
An instrument for measuring minute intervals of time; used in determining the velocity of projectiles, the duration of short-lived luminous phenomena, etc.