Taxy

Part of speech: verb, noun

Definitions

1. Describing an organism's automatic movement toward or away from a stimulus such as light or chemicals
2. Relating to the directed locomotion that a living cell or creature shows in response to an outside signal
3. Characterizing a response in which an organism steers its body toward or away from a particular stimulus

Etymology: "Taxy" is a spelling variant of the verb "taxi," which describes an aircraft rolling along the ground under its own power. The verb comes from the noun, and the noun is a shortening of "taximeter cab." The taximeter was a device that calculated a fare by distance travelled, and its name combines "taxi-" from Medieval Latin "taxa," a charge or assessment, with the Greek-derived "-meter." The Latin root is "taxare," meaning to estimate or charge. Once cab passengers knew the vehicle by its meter, clipping the phrase to "taxi" was a natural step. Pilots later borrowed the shortened noun as a verb for moving an aircraft along a runway, and the spelling "taxy" appears as an alternative form of that verb.