(idiomatic) The practice of flipping a coin in the air, to choose between two alternatives based on which side lands face up.

(now chiefly US) Inconsistent, unpredictable, erratic; sometimes succeeding and sometimes failing.

(mathematics, logic) Of one of a series of models, languages, relationship, forms of logical discourse, etc., being the simplest one or the first in a sequence. / Of fundamental importance.

(chemistry, physics) an atomic or molecular orbital whose energy increases as its constituent atoms are brought closer together - thus generating a repulsive force that hinders bonding

(mathematics, logic) Denoting the second in a numerical sequence of models, languages, relationships, forms of logical discourse etc. / Of secondary importance.

The orbit of a satellite that is nearer the planet than it would be if it were in synchronous orbit

(dated, 17th century) The principles under which the world and its components operate. / The strict enforcement of law, statutes, and social conventions.

A satellite orbit around the Earth within the altitude range of 200 - 2000 km, in which a satellite can communicate with Earth with a small time lag and energy consumption. Abbreviation: LEO.

(music) A large orchestra that traditionally plays Western classical orchestral music.

Alternative form of what the doctor ordered