tacho-, tach-, tachy-

(Greek: fast, speed, swift, rapid)

Appearing or developing suddenly.
A reference to a tongue: capable of being quickly thrust forth and retracted, as that of the ant-eater or snake.
Echidnas (spiny anteater); family containing two or three species of small terrestrial, semifossorial, egg-laying mammals found in Australia and New Guinea.
In zoology, the genus consisting of the typical echidnas (Australian terrestrial anteaters; burrowers with long snouts and tongues).
A tachygraphic manuscript.
tachygrapher, tachygraphist
A writer of shorthand, a stenographer.
1. The shorthand system used by the ancient Greeks and Romans.
2. The abbreviated cursive writing used in medieval times for Latin and Greek.
The art of fast healing.
The abnormal rapidity of speech or talking very quickly.
An abnormal rapidity of speech. It is used loosely to include an excessive amount of talking, which is more properly termed lalorrhea, logodiarrhea, logorrhea, polylogia, or polyphrasia.
An instrument used in surveying to work out distances, elevations, and directions at speed.
Enables the operator, by a single observation upon a rod, to obtain the necessary horizontal and vertical data for the determination of the three elements of position of a point on the surface of the earth.
Hypothetical elementary particles that always travel faster than the speed of light.

Tachyons seem to break all the rules. If they exist—and no one has yet proven that they do—they would not only travel faster than light, but backwards in time, too. In the 1960's a group of physicists decided that Einstein's speed limit did not apply to particles that were already moving faster than light.

Unlike normal particles, a tachyon is thought to gain speed when it loses energy, so a tachyon with zero energy would have infinite speed. In fact, it would require infinite energy to slow a tachyon to the speed of light, making it impossible for it to travel below the speed of light.

Tachyons have been known about since 1967 and were first proposed by physicist Arnold Sommerfeld and coined by the physicist Gerald Feinberg. At first they were dismissed as non-real-by-products of the relativity equations, but now tachyons are turning up in theories everywhere.

It has been suggested that tachyons are produced in cosmic rays, and even that they could account for that mysterious "dark matter". Tachyons also play a role in "string theory", which has brought them back into the spotlight.

—Excerpts from "Tachyons", New Scientist, February, 4, 2006; page 56.
There was a young lady named Bright,
Whose speed was far faster than light.
She went out one day,
In a relative way,
And returned the previous night!
—Reginald Buller
tachyphagia, tachyphagy
1. Rapid or hasty eating; seen in some forms of regressed schizophrenia.
2. Food-grabbing; extreme rapidity of eating. It is commonly seen in regressed, deteriorated schizophrenics, and often such patients will grab any object, edible or not, put it into the mouth, and swallow it.
Excessively fast talking.