An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

1) A danger that one can foresee but cannot avoid.
2) Something causing unavoidable danger, peril, risk, or difficulty.
3) The absence or lack of predictability; chance; uncertainty (Dictionary.com).

M.E. hasard, from O.Fr. hasard, hasart "game of chance played with dice," possibly from Sp. azar "an unfortunate card or throw at dice," postulated to derive from Ar. az-zahr "the die," but this etymology is controversial.

Âpé, from Av. au-pat-, "to fall down, off," from pat- "to fall, fly;" Proto-Ir. *pat- "to fall; fly; rise;" related to Pers. oftâdan "to fall; to befall; to happen," → fall. Pers. âfat "blight, pest, curse," may belong to this family.

1) Full of risk; perilous; risky.
2. Dependent on chance (Dictionary.com).

Adj. from → hazard.

The danger of collision with Earth posed by solar system small bodies that pass near our planet. These objects include → near-Earth asteroids and nuclei of → comets. See also: → near-Earth object, → impact crater, → Torino scale, → Palermo scale, → Space Situational Awareness.

→ impact; → hazard.

An asteroid that could make a threatening close approach to the Earth. In technical terms a PHA is defined as having an → absolute magnitude of 22 or brighter and an → Earth Minimum Orbit Intersection Distance (MOID) of less than 0.05 → astronomical unit or 7.5 million km.

→ potentially; → hazardous; → asteroid.