Emprise

The archaic word emprise may be

• a verb, 'to emprise', meaning 'to undertake', 'to assume the duty or responsibility of', or
• a noun, 'an emprise', or 'an emprize', meaning 'an adventure', 'an undertaking', 'an enterprise'. This is found in medieval writing, and is normally used of knightly conduct - martial prowess, romantic adventure, or renown and glory.

Hart's Rules lays down that emprise should always be spelled thus, with an '-s-'; but OED allows that the noun may be spelled with either '-s-' or '-z-' - a latitude that it doesn't allow to the verb.

See -ise - -ize.