1. North American herb with pungent scaly or toothed roots
   - crinkleroot, crinkle-root, crinkle root, pepper root, toothwort, Cardamine diphylla

Type of: bitter cress, bittercress

• Ornithorhynchidae
• Ornithorhynchus
• Ornithorhynchus anatinus
• ornithosis
• Orobanchaceae
• orogeny
• orography
• oroide
• orology
• Orono
• Orontium
• Orontium aquaticum
• oropharyngeal
• oropharynx
• orotund
• orotundity
• Orozco
• orphan
• orphan site
• orphanage
• orphaned
• orphanhood
• orphans' asylum
• orphenadrine
• Orpheus