thats a fact (adjective) indisputable: beyond doubt
Sinonime: absolute,
accurate,
actual,
certain, double-checked,
evident, incontestable,
incontrovertible,
indubitable,
irrefutable, no ifs ands or buts about it, no mistake, open and shut,
positive,
real,
sure, that's a fact,
true, unassailable,
undeniable, undoubted, unfabled, unquestionable, veridical
Antonime: disputable,
doubtful,
dubious,
indefinite,
questionable, refutable,
uncertain,
unreliable,
unsure,
vague