Selah

Psalms 81
7 Thou calledst in trouble, and I delivered thee; I answered thee in the secret place of thunder: I proved thee at the waters of Meribah. Selah.

Definition Of Selah From Easton
A word frequently found in the Book of Psalms, and also in Hab 3:9, Hab 3:13, about seventy-four times in all in Scripture. Its meaning is doubtful. Some interpret it as meaning "silence" or "pause;" others, "end," "a louder strain," "piano," etc. .

To me it ususlly means 'Hallelujah, Praise the Lord.' But it's not always good substitution.