Synonyms for Downright:

adj.

absolute (adjective)
unqualified, crashing.
artless (adjective)
artless, blunt, broad, callow, candid, direct, frank, genuine, honest, ingenuous, naive, natural, open, outgoing, overt, plain, sincere, straightforward, trusting, unaffected, undisguised, unrestrained, unsophisticated, Plain-spoken, Unartful, Unbeguiling, un-artificial, uncalculating, undeceitful, undeceiving, undeceptive.
complete (adjective)
out-and-out.
direct (adjective)
undisguised.
perfect (adjective)
perfect.
plainspoken (adjective)
plainspoken, Plain-spoken, man-to-man.
positive (adjective)
positive.
thorough, absolute (adjective)
blunt, clear, complete, damned, flat, honest, open, out-and-out, outright, plain, positive, sincere, straight, straightforward, thoroughgoing, total, undisguised, unequivocal, unmitigated, unqualified, utter.

adv.

entirely (adverb)
completely.

n.

good, in depth, resounding, sound. all-out, arrant, big, blooming, consummate, crashing, damned, dead, flat, flat out, fully, limited, outright, perfect, positive, pure, purely, really, thorough, thoroughgoing, thoroughly, total, totally, unbounded, unequivocal, unlimited, unmitigated, unqualified, unrelieved, unreserved, utter, well. clear, forthright, man-to-man, plainspoken, show, straight, straight-out, straight-from-the-shoulder, straight-shooting. downright (noun)
absolute, complete, honest, honorable, out-and-out, rank, right-down, sheer.
frank (noun)
abrupt.
thorough (noun)
thoroughgoing, total, utter.
thoroughly (noun)
absolutely, completely, entirely, utterly.

Other synonyms:

arrant, crashing, man-to-man, plainspoken, straight-out, unrelieved, straight-from-the-shoulder. abrupt, forthright, outright, thoroughgoing, straight-shooting. all-out, consummate, flat out, pure, unbounded, unlimited, unmitigated. blooming, thorough, unequivocal. damned, straight, unreserved. positive. complete, dead, perfect. flat. Other relevant words:
abrupt, absolute, absolutely, all-out, arrant, big, blooming, clear, complete, completely, consummate, crashing, damned, dead, entirely, flat, flat out, forthright, fully, good, honorable, in depth, limited, man-to-man, out-and-out, outright, perfect, plainspoken, positive, pure, purely, rank, really, resounding, right-down, sheer, show, sound, straight, straight-out, thorough, thoroughgoing, thoroughly, total, totally, unbounded, unequivocal, unlimited, unmitigated, unqualified, unrelieved, unreserved, utter, utterly, well, straight-from-the-shoulder, straight-shooting.

Usage examples for downright

  1. One day he pushed my patience beyond all limit, and I grew downright angry with him. – That Boy Of Norcott's by Charles James Lever
  2. There is a sort of defiance of him in stopping; there is a downright concession to him in going away." – Basil by Wilkie Collins
  3. All I did was, I hesitated, and cried, and didn't say 'no, ' downright like a fool. – Put Yourself in His Place by Charles Reade