Halal - to be clear, to shine, to make a show, to boast, to be clamorously foolish, to rave, to celebrate.
This word is used approximately 115 times in the Old Testament. The first time it appears in in 1 Chronicles 15:4 (KJV, emphasis added):
And He appointed certain of the Levites to minister before the ark of the Lord, and to record, and to thank and praise the Lord God of Israel.
To get a better understanding of the context of this verse, let's begin with the first verse:
So they brought the ark of God, and set it in the midst of the tent that David had pitched for it: and they offered burnt sacrifices and peace offerings before God. And when David had made an end of offering the burnt offerings and the peace offerings, he blessed the people in the name of the Lord. And he dealt to everyone of Israel, both man and woman, to every one a loaf of bread, and a good piece of flesh, and a flagon of wine. And he appointed certain of the Levites to minister before the ark of the Lord, and to record, and to thank and praise the Lord God of Israel: Asaph the chief, and next to him Zechariah, Jeiel, and Shemiramoth, and Jehiel, and Mattihiah, and Eliab, and Benaiah, and Obed-edom: and Jeiel with psalteries and with harps; but Asaph made a sound with cymbals; Benaiah also and Jahaziel the priests with trumpets continually before the ark of the covenant of God. (emphasis added)
When David brought the ark of God in the camp,he offered sacrifices to the Lord and set up his own praise team and a band. This praise team and band were to minister, thank, and halal the Lord. They were "to be clear, shine, make a show, boast, act clamorously foolish,rave and celebrate" the Lord.