Unimproved rhymes with:
improved, improved, approved, disapproved, disproved, improved, proved, unapproved, unproved, approved, disapproved, disproved, improved, proved, unapproved, unproved
Unimproved sounds like:
unapproved, unproved, unverified
improved, improved, approved, disapproved, disproved, improved, proved, unapproved, unproved, approved, disapproved, disproved, improved, proved, unapproved, unproved
unapproved, unproved, unverified