1.
An explanation or statement that is ~ seems likely to be true or valid.
A more ~ explanation would seem to be that people are fed up with the Conservative government...
= reasonable
ADJ
plausibly
Having bluffed his way in without paying, he could not plausibly demand his money back.
ADV: ADV with v
plausibility
...the plausibility of the theory.
= credibility
N-UNCOUNT
2.
If you say that someone is ~, you mean that they seem to be telling the truth and to be sincere and honest.
He was so ~ that he conned everybody.
= believable
ADJ