  We consider the class of groups whose word problem is poly-context-free; that
is, an intersection of finitely many context-free languages. We show that any
group which is virtually a finitely generated subgroup of a direct product of
free groups has poly-context-free word problem, and conjecture that the
converse also holds. We prove our conjecture for several classes of soluble
groups, including metabelian groups and torsion-free soluble groups, and
present progress towards resolving the conjecture for soluble groups in
general. Some of the techniques introduced for proving languages not to be
poly-context-free may be of independent interest.
