Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. gibber, ĕra, ĕrum, adj. [like gibbus; kindr. to Sanscr. kubya, hunch-backed; Gr. κυφός, κύπτω], crook-backed, hunch-backed, hump-backed.
2. gibber, ĕris, m. [1. gibber], a hunch or hump on the back (post-Aug.), Plin. 8, 45, 70, § 179: quod erat aucto gibbere, App. Flor. p. 350; cf. also 1. gibbus, II.