Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
fastōsus, a, um, adj. [2. fastus], full of pride, proud, haughty (post-Aug. and rare): moecha, Mart. 10, 13, 7: quid est, fastose? Petr. 131.
Transf., of things: domus, Auct. Pan. ad Pis. 107: garum, Mart. 13, 102, 2.