The Collaborative International Dictionary of English v.0.48:
Oak \Oak\ ([=o]k), n. [OE. oke, ok, ak, AS. [=a]c; akin to D.
eik, G. eiche, OHG. eih, Icel. eik, Sw. ek, Dan. eeg.]
1. (Bot.) Any tree or shrub of the genus Quercus. The oaks
have alternate leaves, often variously lobed, and
staminate flowers in catkins. The fruit is a smooth nut,
called an acorn, which is more or less inclosed in a
scaly involucre called the cup or cupule. There are now
recognized about three hundred species, of which nearly
fifty occur in the United States, the rest in Europe,
Asia, and the other parts of North America, a very few
barely reaching the northern parts of South America and
Africa. Many of the oaks form forest trees of grand
proportions and live many centuries. The wood is usually
hard and tough, and provided with conspicuous medullary
rays, forming the silver grain.
2. The strong wood or timber of the oak.
Note: Among the true oaks in America are:
Barren oak, or
Black-jack, Quercus nigra.
Basket oak, Quercus Michauxii.
Black oak, Quercus tinctoria; -- called also yellow oak
or quercitron oak.
Bur oak (see under Bur.), Quercus macrocarpa; -- called
also over-cup or mossy-cup oak.
Chestnut oak, Quercus Prinus and Quercus densiflora.
Chinquapin oak (see under Chinquapin), Quercus
Coast live oak, Quercus agrifolia, of California; -- also
Live oak (see under Live), Quercus virens, the best of
all for shipbuilding; also, Quercus Chrysolepis, of
Pin oak. Same as Swamp oak.
Post oak, Quercus obtusifolia.
Red oak, Quercus rubra.
Scarlet oak, Quercus coccinea.
Scrub oak, Quercus ilicifolia, Quercus undulata, etc.
Shingle oak, Quercus imbricaria.
Spanish oak, Quercus falcata.
Swamp Spanish oak, or
Pin oak, Quercus palustris.
Swamp white oak, Quercus bicolor.
Water oak, Quercus aquatica.
Water white oak, Quercus lyrata.
Willow oak, Quercus Phellos.
[1913 Webster] Among the true oaks in Europe are:
Bitter oak, or
Turkey oak, Quercus Cerris (see Cerris).
Cork oak, Quercus Suber.
English white oak, Quercus Robur.
Holly oak, or
Holm oak, Quercus Ilex.
Kermes oak, Quercus coccifera.
Nutgall oak, Quercus infectoria.
Note: Among plants called oak, but not of the genus
African oak, a valuable timber tree (Oldfieldia
Australian oak or She oak, any tree of the genus
Casuarina (see Casuarina).
Indian oak, the teak tree (see Teak).
Jerusalem oak. See under Jerusalem.
New Zealand oak, a sapindaceous tree (Alectryon
Poison oak, a shrub once not distinguished from poison ivy,
but now restricted to Rhus toxicodendron or Rhus
Silky oak or Silk-bark oak, an Australian tree
Green oak, oak wood colored green by the growth of the
mycelium of certain fungi.
Oak apple, a large, smooth, round gall produced on the
leaves of the American red oak by a gallfly (Cynips
confluens). It is green and pulpy when young.
Oak beauty (Zool.), a British geometrid moth (Biston
prodromaria) whose larva feeds on the oak.
Oak gall, a gall found on the oak. See 2d Gall.
Oak leather (Bot.), the mycelium of a fungus which forms
leatherlike patches in the fissures of oak wood.
Oak pruner. (Zool.) See Pruner, the insect.
Oak spangle, a kind of gall produced on the oak by the
insect Diplolepis lenticularis.
Oak wart, a wartlike gall on the twigs of an oak.
The Oaks, one of the three great annual English horse races
(the Derby and St. Leger being the others). It was
instituted in 1779 by the Earl of Derby, and so called
from his estate.
To sport one's oak, to be "not at home to visitors,"
signified by closing the outer (oaken) door of one's
rooms. [Cant, Eng. Univ.]