Synonyms of the word

premature

• adj. Occurring before a state of readiness or maturity has arrived.
• adj. Taking place earlier than anticipated, prepared for, or desired.
• adj. (informal) Suffering from premature ejaculation.
• n. An infant born prematurely.

early

• adj. At a time in advance of the usual or expected event.
• adj. Arriving a time before expected; sooner than on time.
• adj. Near the start or beginning.
• adj. Having begun to occur; in its early stages.
• adv. At a time before expected; sooner than usual.
• adv. Soon; in good time; seasonably.
• n. (informal) A shift (scheduled work period) that takes place early in the day.

immature

• adj. Not fully formed or developed, unripe, not mature.
• adj. Childish in behavior, not mature.
• n. An immature member of a species.

previous

• adj. Prior; occurring before something else, either in time or order.
• adj. (informal) Premature; acting or occurring too soon.
• n. (informal, Britain) An existing criminal record (short for "previous convictions"); loosely, a track record…

untimely

• adj. at an inopportune time.
• adj. early; premature.