1. Not open to challenge
   "unchallengeable facts"; "a position of unchallengeable supremacy"

See also: noncontroversial, uncontroversial

• umlaut
• Umma
• Umma Tameer-e-Nau
• Ummah
• ump
• umpirage
• umpire
• umpteen
• umpteenth
• umptieth
• umteen
• umteenth
• UN agency
• un-
• un-American
• un-come-at-able
• una corda
• unabashed
• unabashedly
• unabated
• unable
• unable to help
• unabridged
• unabridged dictionary
• unabused