sursum

• sūrsus
• sūsum, sūsus (through assimilation and degemination)

From su(p)s +‎ vorsum, variants of sub (“under, below”) and versum (“towards, -wards”).

• (Classical) IPA^(key): /ˈsuːr.sum/, [ˈs̠uːrs̠ʊ̃ˑ]
• (Ecclesiastical) IPA^(key): /ˈsur.sum/, [ˈsursum]

sūrsum (not comparable)

1. upwards, up
   • early 6th c., Boethius, Contra Eutychen et Nestorium 1:

     corpus omne habet proprium mōtum, ut ignis sūrsum, terra deorsum.

     Any given body has a movement of its own, such as fire upwards, earth downwards.

2. (rare) above, high up
   • 45 BCE, Cicero, De Natura Deorum 2.56.151:

     nārēs, quod omnis odor ad supera fertur, rēctē sūrsum sunt

     The nose is rightly placed high up since every smell carries itself upwards

• (upwards): deorsum

• sūrsum versum / sursum vorsum
• sūrsuorsum

From the form sūsum:

• “sursum”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
• “sursum”, in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
• sursum in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
• sursum in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette
• Meyer-Lübke, Wilhelm (1911), “sū(r)sum”, in Romanisches etymologisches Wörterbuch (in German), page 638