one-flowered pyrola
— Noun
– English
～ delicate evergreen dwarf herb of north temperate regions having a solitary white terminal flower; sometimes placed in genus Pyrola
optical pyrometer
— Noun
– English
～ a pyrometer that uses the color of the light emitted by a hot object
one-quadrillionth
— Noun
– English
～ one part in a quadrillion equal parts
one-quarter
— Noun
– English
～ one of four equal parts; "a quarter of a pound"
one-quintillionth
— Noun
– English
～ one part in a quintillion equal parts
obstacle race
— Noun
– English
～ a race in which competitors must negotiate obstacles
optic radiation
— Noun
– English
～ a nerve pathway from the lateral geniculate body to the visual cortex
overhead railway
— Noun
– English
～ a railway that is powered by electricity and that runs on a track that is raised above the street level
order Rajiformes
— Noun
– English
～ fish with dorsoventrally flattened bodies; includes: rays; skates; guitarfishes; sawfishes
order Ranales
— Noun
– English
～ herbs, shrubs and trees: includes families Ranunculaceae; Annonaceae; Berberidaceae; Magnoliaceae; Menispermaceae; Myristicaceae; Nymphaeaceae; Lardizabalaceae; Lauraceae; Calycanthaceae; Ceratophyllaceae; Cercidiphyllaceae
omnidirectional range
— Noun
– English
～ a navigational system consisting of a network of radio beacons that provide aircraft with information about exact position and bearing
omnidirectional radio range
— Noun
– English
～ a navigational system consisting of a network of radio beacons that provide aircraft with information about exact position and bearing
order Ranunculales
— Noun
– English
～ herbs, shrubs and trees: includes families Ranunculaceae; Annonaceae; Berberidaceae; Magnoliaceae; Menispermaceae; Myristicaceae; Nymphaeaceae; Lardizabalaceae; Lauraceae; Calycanthaceae; Ceratophyllaceae; Cercidiphyllaceae
order Raptores
— Noun
– English
～ term used in former classifications; erroneously grouped together birds of the orders Falconiformes and Strigiformes
opossum rat
— Noun
– English
～ terrestrial marsupials of southern South America that resemble shrews
Ord kangaroo rat
— Noun
– English
～ most widely distributed kangaroo rat: plains and mountain areas of central and western United States
occupancy rate
— Noun
– English
～ the percentage of all rental units (as in hotels) are occupied or rented at a given time
octane rating
— Noun
– English
～ a measure of the antiknock properties of gasoline
Ockham's Razor
— Noun
– English
～ the principle that entities should not be multiplied needlessly; the simplest of two competing theories is to be preferred