safetyEnglishOxford American Thesaurussafety noun 1 she is still driving too fast for the safety of local residents: welfare, well-being, protection, security. ▷antonyms danger. 2 research into the safety of roll-on roll-off ferries: security, soundness, secureness, dependability, reliability, impregnability. 3 they had to reach the safety of open water: shelter, sanctuary, refuge. 4 the safety of medicines: harmlessness, lack of side effects.