Unassailable is an adjective that means something that cannot be attacked or defeated. There are various synonyms for this word that convey the same sense of invincibility. Words like impregnable, invulnerable, unbeatable, bulletproof, and indomitable are all synonyms for unassailable. Other synonyms for unassailable include unbreakable, insurmountable, unshakable, untouchable, and unconquerable. These words can be used interchangeably to describe something that is impervious to harm or destruction. Overall, the word unassailable implies a sense of strength and superiority that cannot be contested or challenged.