I. trust ‧ y 1 /ˈtrʌsti/ BrE AmE adjective [only before noun]
[ Word Family: adjective : ↑ trusting , ↑ trustworthy ≠ ↑ untrustworthy , ↑ trusty , ↑ distrustful , ↑ mistrustful ; noun : ↑ trust ≠ ↑ distrust ≠ ↑ mistrust , ↑ trustee , ↑ trusteeship , ↑ trustworthiness ; verb : ↑ trust ≠ ↑ distrust ≠ ↑ mistrust ]
old-fashioned a trusty weapon, vehicle, animal etc is one that you have had for a long time and can depend on – often used humorously SYN reliable :
He had his trusty old penknife with him.
II. trusty 2 BrE AmE noun ( plural trusties ) [countable] British English
a prisoner who is given special jobs or rights, because they behave in a way that can be trusted