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The initial movement by which or the instant in which a rocket or other such craft commences flight.
1. (Astronautics) the initial movement or ascent of a rocket from its launch pad
2. (Astronautics) the instant at which this occurs
(Astronautics) (intr, adverb) (of a rocket) to leave its launch pad
1. the action of an aircraft in becoming airborne or of a rocket in rising from its launching site under its own power.
2. the instant when such action occurs.