calculable fail-safe faithful faithworthy fast firm guaranteed harmless incorruptible invincible inviolable invulnerable predictable proven reliable responsible riskless secure solid sound stable staunch steadfast steady straight substantial sure surefire tested to be trusted tried tried and true TRUE trustable trustworthy trusty undangerous unfailing unfalse unhazardous unperfidious unperilous unprecarious unrisky untreacherous warranteed well-founded well-grounded