| DROMOPHOBIA | • DROMOPHOBIA n. a fear of crossing streets. |
| ODORIPHORES | • ODORIPHORE n. the group of atoms in an odorous molecule responsible for its odour. |
| ORCHIDOLOGY | • orchidology n. The study of orchids. • ORCHIDOLOGY n. the study of orchids. |
| ORNITHOPODS | • ornithopods n. Plural of ornithopod. • ORNITHOPOD n. a member of a suborder of bipedal ornithischian (bird-hipped) dinosaurs. |
| ORTHODONTIA | • orthodontia n. Synonym of orthodontics. • ORTHODONTIA n. the rectification of crookedness in the teeth, also ORTHODONTICS. |
| ORTHODONTIC | • orthodontic adj. Of, or relating to the dental speciality of orthodontics. • ORTHODONTIC adj. relating to orthodontics, the rectification of crookedness in the teeth. |
| ORTHODOXIES | • orthodoxies n. Plural of orthodoxy. • ORTHODOXY n. the state of being orthodox. |
| ORTHODROMIC | • orthodromic adj. Of or relating to a means of navigation by following an arc of the great circle corresponding to the… • orthodromic adj. (Of neurons) Passing along neurological impulses in a normal (expected) direction. • ORTHODROMIC adj. having great circles represented as straight lines. |
| PHOTOPERIOD | • photoperiod n. (Biology) The normal duration of natural daylight experienced by an organism; daylength. • PHOTOPERIOD n. the period during every 24 hours when an organism is exposed to daylight. |
| RADIOPHOTOS | • radiophotos n. Plural of radiophoto. • RADIOPHOTO n. a picture transmitted by radio. |
| RHIZOPODOUS | • rhizopodous adj. (Zoology) Of or pertaining to the rhizopods. • RHIZOPODOUS adj. relating to a rhizopod. |
| TRAITORHOOD | • traitorhood n. The quality of being a traitor. • TRAITORHOOD n. the state of being a traitor. |
| WIDOWERHOOD | • widowerhood n. The state or period of being a widower. • WIDOWERHOOD n. the fact or state of being a widower. |