premature (adj.)
- advanced
- beforehand
- early
- forward
- green
- half-baked
- hasty
- ill-considered
- ill-timed
- immature
- improper
- impulsive
- inappropriate
- inauspicious
- inconvenient
- inexpedient
- infelicitous
- inopportune
- intrusive
- irrelevant
- late
- malapropos
- overhasty
- precipitate
- precocious
- previous
- rushed
- unbefitting
- uncrystallized
- underdeveloped
- undeveloped
- unfavorable
- unfit
- unfitting
- unfledged
- unfortunate
- unhappy
- unlucky
- unpremeditated
- unprepared
- unpropitious
- unready
- unripe
- unseasonable
- unsuitable
- untimely
- untoward
- wrong
