Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Perseus.
The word Deïoneus could not be parsed. Trying a normal dictionary lookup:
No entries found. Showing closest matches:
Dēīŏnĭdes, ae, m., Δηϊονίδης, son of Deïone by Apollo, i. e. Miletus, Ov. M. 9, 442.