gullible /ˈɡʌlɪbl̩/adjective 1noun 1forms 3 adjective1 •Easily deceived or duped; naive, easily cheated or fooled.Andrew is so gullible, the way he still believes in Santa Claus, the Easter Bunny, the Tooth Fairy, and the Sandman at the age of fourteen. noun1 •A gullible person; someone easily fooled or tricked.Spurious accounts that snare the gullible are readily available. Skeptical treatments are much harder to find. — 1995 formsgullibles · more gullible · most gullible