rictus /rikˈtəs/ (zoology)

1. The gape, esp of a bird
2. The chink or aperture of a lipped corolla
3. Unnatural gaping of the mouth, eg in horror

• psychobiological
• psychobiologies
• psychobiologist
• psychobiologists
• psychobiology
• psychochemical
• opera glass
• opera glasses
• opera hat
• opera hats
• opera house
• opera houses
• operand
• operands
• operant
• operant conditioning
• operants
• operas
• opera seria
• opera singer
• opera singers
• operate
• operated
• operates
• operatic