adjective.
Capable of being presumed or taken for granted; reasonable as a supposition.
The Century Dictionary and Cyclopedia
Capable of being presumed or taken for granted; such as may be supposed to be true or entitled to belief without examination or direct evidence, or on probable evidence.
the GNU version of the Collaborative International Dictionary of English
adjective.
Such as may be presumed or supposed to be true; that seems entitled to belief without direct evidence.