That is a matter of opinion; not certain; debatable, conjectural. Also occasionally as n. Now chiefly archaic.

Of the nature of, or expressing, an opinion; founded on opinion; conjectural, uncertain.

= opinable, adj. Also as n.: an object of opinion.

Conjectural; of the nature of an opinion rather than fact; = opinative, adj. 1, opinionative, adj. 2. Obsolete.

Based on opinion or belief; imagined; conjectural. = opinative, adj. 1, opiniative, adj. 2, opinionate, adj. 1. Obsolete.