改嫁

改嫁 specifically applies to women — 改 'change' + 嫁 'a woman marries' (literally, 'be given to a household'). For men remarrying, the parallel verb is 续弦 (xùxián, 'replace the broken zither string', poetic) or simply 再婚 (zàihūn, 'remarry', gender-neutral). In imperial-era Confucian thought, widow chastity (寡妇守节) was idealized and 改嫁 carried social stigma — the Song-dynasty Neo-Confucians especially condemned it. Modern law and society treat it as a matter-of-fact choice.

Don't use 改嫁 for a man taking a new wife; it sounds wrong. Default to gender-neutral 再婚 if you're not sure.