Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
laetābundus, a, um, adj. [laetor], greatly rejoicing, full of joy, joyful (post-class.): laetabundus is dicitur, qui abunde laetus est, Gell. 11, 15, 8: his dictis, Mart. Cap. 1, § 23; Vulg. Isa. 35, 2.