reliable

Etymology

rely + -able

adj

1. Suitable or fit to be relied on; worthy of dependence, reliance or trust; dependable, trustworthy
   a reliable witness to the truth of the miracles 1855, Andrews Norton, Internal Evidences of the Genuineness of the Gospels
   the best means, and the most reliable pledge, of a higher object February 18, 1800, Samuel Taylor Coleridge, Report on Mr. Pitt's Speech in Parliament of February 17, 1800, on the Continuance of the War with France (published in The Morning Post)
2. (signal processing, of a communication protocol) Such that either a sent packet will reach its destination, even if it requires retransmission, or the sender will be told that it didn't

noun

1. Something or someone reliable or dependable
   the old reliables