1. Having a relatively tough outer covering 
2. Insensitive to criticism
   - thick-skinned

See also: insensitive, tough

• omnipresent
• omnirange
• omniscience
• omniscient
• omnium-gatherum
• omnivore
• omnivorous
• Omomyid
• Omomyid group
• omophagia
• Omotic
• omphalocele
• omphalos
• omphaloskepsis
• Omphalotus
• Omphalotus illudens
• omphalus
• Omsk
• on
• on a higher floor
• on a lower floor
• on a regular basis
• on a roll
• on air
• on all fours