An Aramaic verb meaning to be presumptuous, act insolently, or act with arrogance. It describes the willful, defiant attitude of one who acts beyond legitimate bounds — presuming on God's mercy or defying his authority deliberately. The related Hebrew root zid describes intentional, willful sin as opposed to sins of ignorance.
The distinction between unintentional sins and presumptuous sins runs deep through biblical law. Numbers 15 makes clear that intentional, high-handed rebellion — sinning 'with a high hand' — was categorically different from sin committed in ignorance. The presumptuous person sins knowing it is sin, in defiance. This is why Psalm 19 prays 'keep your servant from presumptuous sins.' The frightening implication is that habitual willful sinning hardens the heart and eventually reaches a point where repentance itself becomes difficult. Grace remains, but presuming on it is itself a form of spiritual danger.