1. (informal) scatterbrained, silly
   - ditsy [N. Amer]

Derived forms: ditzier, ditziest

• genus Oleandra
• genus Olearia
• genus Olfersia
• genus Oligoplites
• genus Oligoporus
• genus Ommastrephes
• genus Omphalotus
• genus Oncidium
• genus Oncorhynchus
• genus Ondatra
• genus Oniscus
• genus Onobrychis
• genus Onoclea
• genus Ononis
• genus Onopordon
• genus Onopordum
• genus Onosmodium
• genus Onychium
• genus Onychogalea
• genus Onychomys
• genus Opheodrys
• genus Ophiodon
• genus Ophioglossum
• genus Ophiophagus
• genus Ophisaurus