adventitious C2+

/ˌædvɛnˈtɪʃəs/ arising from an external or accidental cause rather than inherently

peradventure C2+

/ˌpɜrədˈvɛntʃər/ perhaps or possibly; uncertainty or doubt (archaic)

disadventurous C2+

/ˌdɪsədˈvɛntʃərəs/ archaic term for unfortunate, unlucky, or marked by misadventure

venturesome C2+

/ˈvɛntʃɚsəm/ willing to take risks; daring and adventurous