According to Osho, 'spirit' refers to disembodied souls lingering between lives—extremes of evil become bhutas/pretas (ghosts), extremes of goodness become devas (divine beings)—while the ordinary quickly reincarnate and do not become spirits. He does not equate this with an 'astral body,' which would be a subtle vehicle; here, 'spirit' names a temporary in-between condition.
A spirit is a soul stuck between births (as a ghost or a deva), not the subtle astral body itself.