1. A person or thing that provides direction, information, or advice that cannot be trusted or depended upon; something that leads one astray
The old map proved to be an unreliable guide through the forest.
O mapa antigo se mostrou um guia pouco confiável pela floresta.
2. Information or instructions that are inaccurate, inconsistent, or misleading
His emotions were an unreliable guide to making rational decisions.
Suas emoções eram um guia pouco confiável para tomar decisões racionais.