Manful, a.
Showing manliness, or manly spirit; hence, brave, courageous, resolute, noble. " Manful hardiness." Chaucer. -- Man"ful*ly, adv. -- Man"ful*ness, n.
Shades of meaning
Fernald has no entry of its own for manful; he lists it under masculine.
Where he writes about it:
Manly refers to all the qualities and traits worthy of a man; manful, especially to the valor and prowess that become a man; we speak of a manful struggle, manly decision; we say manly gentleness or tenderness; we could not say manful tenderness. — from masculine