viva voce
Concise Oxford English Dictionary © 2008 Oxford University Press:
viva voce /ˌvʌɪvə ˈvəʊtʃeɪ, ˈvəʊtʃi/
▶adjective (especially of an examination) oral rather than written. ▶adverb orally rather than in writing. ▶noun Brit. full form of viva1.
– origin C16: from med. L., lit. ‘with the living voice’.
'viva voce' also found in these Oxford entries:

