(astronomy) any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light
planet
Noun
any celestial body (other than comets or satellites) that revolves around a star
planet
Noun
a person who follows or serves another
planetary nebula
Noun
a nebula that was once thought to be a star with its planets but is now thought to be a very hot star surrounded by an expanding envelope of ionized gases that emit a fluorescent glow because of intense radiation from the star
planetesimal
Noun
one of many small solid celestial bodies thought to have existed at an early stage in the development of the solar system
plasmid
Noun
a small cellular inclusion consisting of a ring of DNA that is not in a chromosome but is capable of autonomous replication
plasmid DNA
Noun
a small cellular inclusion consisting of a ring of DNA that is not in a chromosome but is capable of autonomous replication
pack ice
Noun
a large expanse of floating ice
pallasite
Noun
a meteorite composed principally of olivine and metallic iron
pebble
Noun
a small smooth rounded rock
peneplain
Noun
a more or less level land surface representing an advanced stage of erosion undisturbed by crustal movements
peneplane
Noun
a more or less level land surface representing an advanced stage of erosion undisturbed by crustal movements
peninsula
Noun
a large mass of land projecting into a body of water
permafrost
Noun
ground that is permanently frozen
petrifaction
Noun
a rock created by petrifaction
petrifaction
Noun
the process of turning some plant material into stone by infiltration with water carrying mineral particles without changing the original shape
photoelectron
Noun
an electron that is emitted from an atom or molecule by an incident photon
photon
Noun
a quantum of electromagnetic radiation
photosphere
Noun
the intensely luminous outer surface of a star, usually referring to the sun
piedmont
Noun
a gentle slope leading from the base of a mountain to a region of flat land
pinetum
Noun
an area planted with pine trees or related conifers
polar glacier
Noun
a glacier near the Arctic or Antarctic poles
pole star
Noun
the brightest star in Ursa Minor
polar star
Noun
the brightest star in Ursa Minor
polestar
Noun
the brightest star in Ursa Minor
polder
Noun
low-lying land that has been reclaimed and is protected by dikes (especially in the Netherlands)
polynya
Noun
a stretch of open water surrounded by ice (especially in Arctic seas)
pond
Noun
a small lake
positron
Noun
an elementary particle with positive charge
pothole
Noun
a pit or hole produced by wear or weathering (especially in a road surface)
precipice
Noun
a very steep cliff
prion
Noun
(microbiology) an infectious protein particle similar to a virus but lacking nucleic acid
promontory
Noun
a natural elevation (especially a rocky one that juts out into the sea)
protein molecule
Noun
any large molecule containing chains of amino acids linked by peptide bonds
proton
Noun
a stable particle with positive charge equal to the negative charge of an electron
ptyalith
Noun
calculus in a salivary gland
pulsar
Noun
a degenerate neutron star
plateau
Noun
a relatively flat highland
prime mover
Noun
an agent that is the cause of all things but does not itself have a cause
primum mobile
Noun
an agent that is the cause of all things but does not itself have a cause
phoenix
Noun
a large monocotyledonous genus of pinnate-leaved palms found in Asia and Africa
phoenix
Noun
a legendary Arabian bird said to periodically burn itself to death and emerge from the ashes as a new phoenix
peri
Noun
(Persian folklore) a supernatural being descended from fallen angels and excluded from paradise until penance is done
peri
Noun
a beautiful and graceful girl
pixie
Noun
(folklore) fairies that are somewhat mischievous
pixie
Noun
creeping evergreen shrub having narrow overlapping leaves and early white star-shaped flowers
pixy
Noun
fairies that are somewhat mischievous
pixy
Noun
creeping evergreen shrub having narrow overlapping leaves and early white star-shaped flowers
poltergeist
Noun
a ghost that announces its presence with rapping and the creation of disorder