Adjective
old
Noun
Any
of
a
class
of
aromatic
heterocyclic
compounds
containing
a
ring
of
four
carbon
atoms
,
two
double bonds
and
an
oxygen
atom
;
especially
the
simplest
one
,
C
<
sub
>
4
sub
>
H
<
sub
>
4
sub
>
O
.