to blurt out: to let a promise escape the lips before the mind has weighed it
This verb turns up once in the whole Hebrew Bible, in a proverb about vows. It is a trap, the proverb says, for a person to cry "Holy!" and only afterward look into what has been promised. Calling something holy handed it over to God and put it out of ordinary use, so a single word spoken in a burst of enthusiasm could cost a family a field, a flock, or a year's income.
The point is not the vow itself but the gap between the mouth and the mind. The word names the instant the promise gets out, and the second half of the verse supplies what should have come first, sitting down to work out what the pledge will actually take. Israel's wisdom writers come back to this warning often, telling worshippers not to be hasty with the mouth before God and not to drag their feet paying what they have promised (Ecclesiastes 5:2 to 5; Deuteronomy 23:21 to 23).
The same three letters elsewhere name gulping something down (לוּעַ) and the throat that does the gulping (לֹעַ). Whether blurting is a natural stretch of that picture, the throat working in the other direction, or a separate word that merely looks the same, is still unsettled. The nearest word in plain meaning is another verb for speaking without thinking (בָּטָה), used of a hasty oath, of Moses letting words slip at the waters of Meribah, and of talk that stabs like a sword.