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Also called minor planet. Astronomy. any of the thousands of small bodies of from 480 miles (775 km) to less than one mile (1.6 km) in diameter that revolve about the sun in orbits lying mostly between those of Mars and Jupiter.
Zoology. an asteroidean; a starfish.
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Contemporary Examples

The answer: by watching the asteroid directly pass in front of a star, which is called occultation.
Chariklo, a Minor Planet Nicknamed a “Centaur,” Discovered to Have Rings Matthew R. Francis April 5, 2014

What would it take to carry people to the Moon, or Mars, or an asteroid?
To Infinity and Beyond! NASA’s Orion Mission Blasts Off Matthew R. Francis December 3, 2014

His game lasts until his final ship has either collided with an asteroid or lost a shootout with an enemy saucer.
‘Asteroids’ & The Dawn of the Gamer Age David Owen November 28, 2014

The Tunguska asteroid event was so unusual that witnesses believed it was a visitation from a vengeful god.
10 Bizarre Natural Disasters The Daily Beast May 31, 2010

A majority of these meteorites comes from collisions in the asteroid belt between Mars and Jupiter.
New York City Stages Largest Meteorite Auction Ever Lizzie Crocker October 9, 2012

Historical Examples

The question was, would the Connie try to set his ship down on the asteroid?
Rip Foster in Ride the Gray Planet Harold Leland Goodwin

But the mechanism controlling the asteroid’s invisibility was not destroyed.
The Bluff of the Hawk Anthony Gilmore

Now there was only one thin pair of wires stretching between his ship and the drill on the asteroid.
Anchorite Randall Garrett

Anything that kept them from selling an asteroid must be terrible indeed.
The Planetoid of Peril Paul Ernst

And they were doing a little target practice with plastic bubbles only a few miles above the asteroid.
Acid Bath Vaseleos Garson

noun
Also called minor planet, planetoid. any of numerous small celestial bodies that move around the sun mainly between the orbits of Mars and Jupiter. Their diameters range from 930 kilometres (Ceres) to less than one kilometre
Also called asteroidean (ˌæstəˈrɔɪdɪən). any echinoderm of the class Asteroidea; a starfish
adjective
of, relating to, or belonging to the class Asteroidea
shaped like a star
n.

1802, coined probably by German-born English astronomer William Herschel (1738-1822) from Greek asteroeides “star-like,” from aster “star” (see astro-) + -eidos “form, shape” (see -oid).
asteroid
(ās’tə-roid’)
Any of numerous small, often irregularly shaped rocky bodies that orbit the Sun primarily in the asteroid belt, a region between the orbits of Mars and Jupiter. Asteroids are intermediate in size between planets and meteoroids; the largest asteroid in the asteroid belt is Ceres, approximately 1,000 km (620 mi) in diameter, while the lower limit is variously given in the tens or hundreds of meters. While more than 1,800 asteroids have been cataloged, and as many as a million or more smaller ones may exist, their total mass has been estimated to be less than three percent of the Moon’s. Asteroids are thought to be left over from the early formation of the solar system, when planetesimals in a protoplanetary disk were scattered after coming under Jupiter’s gravitational influence. The continuing collision of planetesimals that remained between Jupiter and Mars caused many of them to fragment, creating the asteroids that exist today. Also called minor planet, planetoid.
asteroid [(as-tuh-royd)]

A small planet that revolves around the sun. The largest asteroid is only about six hundred miles in diameter. (See asteroid belt.)