- firm, steadfast, steady, unbendable, unfaltering, unshakable, unwavering - marked by firm determination or resolution; not shakable; "firm convictions"; "a firm mouth"; "steadfast resolve"; "a man of unbendable perseverence"; "unwavering loyalty"
Antonym: irresolute (indirect, via resolute)
- level, unwavering - not showing abrupt variations; "spoke in a level voice"; "she gave him a level look"- Louis Auchincloss
Antonym: unsteady (indirect, via steady)