Noah Webster
Definable
DEFINABLE, adjective
1. Literally, that may be limited, or have its limits ascertained. Hence, capable of having its extent ascertained with precision; capable of being fixed and determined. The extent of the Russian empire is hardly definable The limits are hardly definable
2. That may be defined or described; capable of having its signification rendered certain, or expressed with certainty or precision; as definable words.
3. That may be fixed, determined or ascertained; as, the time or period is not definable