Definition of underdraw:
(v) :
To sketch a work of art in chalk, pencil, or other temporary medium prior to painting, inking, or otherwise making the final work.
(v) :
(transitive) To represent inadequately in an artistic depiction, or in words.
(v) :
(transitive) To cover or line the underside of (a floor or roof) with plasterwork, boarding or other such treatment.
(v) :
To take or draw less than one needs or is entitled to.