Learner's definition of RELIABLE
[more reliable; most reliable]
able to be trusted to do or provide what is needed
able to be relied on
able to be believed
likely to be true or correct
a reliable witness
It's a rumor, but I heard it from a reliable source. [=someone who is likely to have accurate information]
We can't write a report without reliable data.
We need more reliable information before we can take action.