Antonyms of adventurous :
unadventurous, safe, afraid, cringing, fearful, pusillanimous, timid, cowardly, faint-hearted, frightened, shrinking, timorous, chickenhearted, coward, craven, lily-livered, milk-livered, milky, poltroon, shy, careful, cautious, heedful, prudent, wary, overcareful, overcautious, affrighted, alarmed, fainthearted, horrified, scared, shocked, spooked, startled, terrified, terrorized, unnerved, calm, cool, levelheaded, rational, reasonable, sage, sane, sensible, sound, wise, appalled, concerned, dismayed, upset, worried, unenterprising.
Examples of usage:
He therefore sought to divert their thoughts from the subject by sitting down and relating many anecdotes connected with his own adventurous history, while they partook of a meal of which they stood much in need. "Sunk at Sea", R.M. Ballantyne.
At rare intervals an islander, by temperament more adventurous or enterprising than his fellows, makes the daring undertaking of a visit to Monnikendam, or the bolder flight to Amsterdam, although there are but few instances on record of such a reckless proceeding as the last. "Odd Bits of Travel with Brush and Camera", Charles M. Taylor, Jr..
He who became a soldier of the cross was free upon his return, and many were adventurous enough to purchase liberty at so honorable a price. "Project Gutenberg History of The Netherlands, 1555-1623, Complete", John Lothrop Motley.