(mathematics, in two dimensions) Describing a simple spiral that starts at a point at the origin and does not divide the plane / (mathematics, in three dimensions) Describing a section of a simple helix

(mathematics, in two dimensions) Describing a double spiral that starts at the origin and divides the plane into two

(mathematics, in two dimensions) Describing a multiple spiral that starts at the origin and divides the plane into multiple regions

A fast or quick start, as to a race.

plural of start codon

(astronautics) An explosion in a rocket engine during startup, usually due to the presence of too much propellant prior to ignition.

(intransitive) To rise suddenly. / (transitive, intransitive) To begin to operate. / (intransitive, colloquial) To begin.

simple past tense and past participle of start up

present participle of start up

(idiomatic) A new beginning, without prejudices.