There are several synonyms for the word "in-susceptible," which means immune or resistant to something. Some of these synonyms include invulnerable, impervious, unaffected, immune, unresponsive, and insusceptible. Each of these words carries a slightly different meaning, but all convey a sense of protection or resistance. For example, invulnerable implies a complete lack of vulnerability, while impervious suggests an inability to be affected by something. Unaffected indicates that no impact has been made, while immune specifically refers to a resistance to disease or infection. Regardless of which synonym is used, all convey a sense of strength and resilience.