[in.fal.li.ble] adj [ME, fr. ML infallibilis, fr. L in- + LL fallibilis fallible] (15c) 1: incapable of error: unerring "an ~ memory"
2: not liable to mislead, deceive, or disappoint: certain "an ~ remedy"
3: incapable of error in defining doctrines touching faith or morals -- in.fal.li.bil.i.ty n -- in.fal.li.bly adv