Definition (full): to loosen, to expose, dismiss, absolve, begin
Strong's Exhaustive Concordance
A primitive root; to loosen; by implication, to expose, dismiss; figuratively, absolve, begin -- avenge, avoid, bare, go back, let, (make) naked, set at nought, perish, refuse, uncover.
KJV: And Moses said unto Aaron, and unto Eleazar and unto Ithamar, his sons, Uncover not your heads, neither rend your clothes; lest ye die, and lest wrath come upon all the people: but let your brethren, the whole house of Israel, bewail the burning which the LORD hath kindled.
NASB: Then Moses said to Aaron and to his sons Eleazar and Ithamar, "Do not uncover your heads nor tear your clothes, so that you will not die and that He will not become wrathful against all the congregation. But your kinsmen, the whole house of Israel, shall bewail the burning which the LORD has brought about.