debuisse
debuisse is a Latin form of debeo, meaning “owe; ought, must”. It is the perfect active infinitive.
Found 63 times in the Latin texts on Socratos.
Where it is used
Caesar, De Bello Gallico 6.42.1: Reversus ille eventus belli non ignorans unum, quod cohortes ex statione et praesidio essent emissae, questus ne minimo quidem casu locum relinqui debuisse, multum fortunam in repentino hostium adventu potuisse iudicavit,
Aulus Gellius, Noctes Atticae 1.7.3: Videbatur compluribus in extremo verbo menda esse. Debuisse enim scribi putabant non futurum, sed futuram, neque dubitabant quin liber emendandus esset, ne, ut in Plauti …
All forms of debeo (conjugation table)
Source: Socratos (socratos.org), a free reader for Ancient Greek and Latin. Grammar from the Perseus Treebank and Morpheus; dictionary entries from Lewis & Short, A Latin Dictionary (Perseus Digital Library, CC BY-SA). Counts are from the texts on Socratos.