from
The Collaborative International Dictionary of English v.0.48
filbert \fil"bert\, n. [Perh. fr. fill + bread, as filling the
bread or husk; cf. G. bartnuss (lit., bread nut) filbert; or
perh. named from a St.Philibert, whose day, Aug. 22, fell in
the nutting season.]
1. (Bot.) The fruit of the {Corylus Avellana} or {Corylus
maxima}, also called the hazel; the hazelnut. It is an
oval nut, containing a kernel that has a mild,
farinaceous, oily taste, agreeable to the palate.
[1913 Webster]
Note: In England filberts are usually large hazelnuts,
especially the nuts from selected and cultivated trees.
The American hazelnuts are of two other species,
{Corylus Americana} and {Corylus cornuta}, and are also
sometimes called filberts.
[1913 Webster +PJC]
2. (Bot.) The tree bearing the filbert; the hazelnut tree.
[PJC]
{Filbert gall} (Zool.), a gall resembling a filbert in form,
growing in clusters on grapevines. It is produced by the
larva of a gallfly ({Cecidomyia}).
[1913 Webster]