"And David danced before the LORD with all his might; and David was girded with a linen ephod."
"Then David returned to bless his household. And Michal the daughter of Saul came out to meet David, and said, How glorious was the king of Israel today, who uncovered himself today in the eyes of the handmaids of his servants, as one of the vain fellows shamelessly uncovereth himself!"
- 2Samuel 6:14,20(KJV)
In verse 16 it says that when Michal saw David "leaping and dancing before the LORD" that she "despised him in her heart".
In her speech to him, where she says '...as one of the vain fellows', according to Strong's this word means,
H7386
רק ריק
rêyq rêq
rake, rake
From H7324; empty; figuratively worthless: - emptied (-ty), vain (fellow, man).
It is similar to Raca, in Matthew chapter 5,
G4469
ῥακά
rhaka
rhak-ah'
Of Chaldee origin (compare [H7386]); O empty one, that is, thou worthless (as a term of utter vilification): - Raca.