Obsidian rhymes with:
antemeridian, ceridian, davidian, didion, floridian, gideon, meridian, meridien, providian, accordion, akkadian, amerindian, andean, antemeridian, arcadian, burgundian, cambodian, canadian, ceridian, chadian, circadian, claudian, collodion, comedian, custodian, davidian, didion, edwardian, floridian, freudian, garabedian, gedeon, gideon, gordian, guardian, indian, macfadyen, madyun, mcfadyen, median, meridian, meridien, mooradian, mouradian, nalbandian, nickelodeon, odeon, odiaun, pancanadian, providian
Obsidian sounds like:
obfuscation, objection, opposition