free base (noun) base on balls: free advance to first base
Sinonime: apparently, as likely as not, as the case may be, assumably, believably, dollars to doughnuts, doubtless, expediently, feasibly, imaginably, in all likelihood, in all probability, like enough,
maybe, most likely, no doubt, one can assume, perchance,
perhaps, plausibly,
possibly, practicably, presumably, presumptively, reasonably, seemingly, to all appearances
Antonime: improbably, unlikely