1. Serving to support or corroborate
   - collateral, confirmative, confirming, confirmatory, corroborative, substantiating, substantiative, validating, validatory, verificatory, verifying

See also: corroborate, supportive

• back off
• back out
• back passage
• back porch
• back to front
• back tooth
• back-alley
• back-formation
• back-geared
• back-number
• back-street
• back-to-back
• backache
• backband
• backbeat
• backbench
• backbencher
• backbend
• backbite
• backbiter
• backblast
• backblocks
• backboard
• backbone
• backbreaking