ChristianAnswers.Net WebBible Encyclopedia

selah

a word frequently found in the Book of Psalms, and also in Hab. 3:9, 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. The LXX render the word by daplasma i.e., “a division.”