That may be depended on; in which one can put reliance, confidence, or trust; certain, sure.

Truthful, true; sure, reliable. Obsolete.

Sure, unerring, not liable to fail; to be depended upon; wholly trustworthy or reliable.

Of a material object: reliable, dependable. Also figurative.

Reliable, certain, sure. Obsolete.

Of a means or method: that may be relied on to attain an intended end; certain to produce the desired or stated result; unfailing, unerring.

Infallible, positive, certain. †Also as adv.

Incapable of failing; sure, reliable.

= infallible, adj. (Common 1530–1620.)

Not liable to fail; unfailing; reliable; infallible.

That may be relied on. Of a person, information, etc.: able to be trusted; in which reliance or confidence may be placed; trustworthy, safe, sure.

Absolutely dependable or reliable; completely trustworthy. Cf. sure, adj. 5a. Obsolete.

Of a person, a person's character, action, words, etc.: that may be believed or relied on; trustworthy, veracious; reliable, dependable.

Of things: Not liable to fail, unfailing. That cannot fail to be, or to come; certain.

Fully demonstrated, tested, or tried; (hence) reliable, trustworthy.

Infallible.

Not liable to fail.

Of an argument, venture, etc.: not liable to fail; reliable.

Originally South Asian or in South Asian context: sure, certain, reliable; genuine, bona fide, correct. Hence more generally: real, not sham; (of…