Green’s Dictionary of Slang

gutsball adj.

[guts ball n. (2)]

(US) plucky, courageous.

[US]K. Kesey Sometimes a Great Notion 30: Just like the corny, gung-ho, guts-ball posters that I seen a good thousand of [HDAS].
G.C. Wilson Supercarrier 103: A guts-ball decision [HDAS].