Definition of frankest:
(adj) :
Honest, especially in a manner that seems slightly blunt; candid; not reserved or disguised.
(adj) :
(medicine) Unmistakable, clinically obvious, self-evident.
(n) :
(uncountable) Free postage, a right exercised by governments (usually with definite article).
(v) :
(transitive) To exempt from charge for postage, as a letter, package, or packet, etc.
(v) :
(transitive) To place a frank on an envelope.
(n) :
(countable) The notice on an envelope where a stamp would normally be found.