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astrodome a transparent dome mounted on the top of an aircraft fuselage to facilitate the use of navigational or astronomical instruments.
astrolabe an instrument used by the ancient Greeks and medieval Arabs to determine the position of heavenly bodies, later replaced by the sextant.
astrology the study of the positions of the heavenly bodies in relation to each other with the aim of predicting their influence on human affairs.
astronaut a person trained to participate in space flight.
astronautics (used with a sing. verb) the science and technology of space travel.
astronomer a scientist who studies the universe beyond the earth.
astronomical of or pertaining to astronomy. [2 definitions]
astronomical unit a unit of length based on the average distance of the earth from the sun, equal to about 149.6 million kilometers or ninety-three million miles.
astronomical year a unit of time equal to the period between one vernal equinox and the next.
astronomy the branch of science concerned with the physical universe beyond the atmosphere of the earth.
astrophotography the photographing of astronomical objects.
astrophysics (used with a sing. verb) the branch of physics that deals with the physical and chemical properties of heavenly bodies and interstellar space.
astute keen in understanding and judgment; shrewd.
Asunción the capital of Paraguay.
asunder in or into separate parts or pieces. [2 definitions]
as usual in the usual way; as always.
as well in addition; also; too.
as well as and also; and moreover. [2 definitions]
as yet up until now.
asylum an institution for the care of those who are unable to maintain themselves, such as orphans or the severely mentally ill. [3 definitions]
asymmetric different, esp. in arrangement of space, on either side of a center line; not symmetrical; unbalanced.