מִכְתָּםmiktâm

Mikhtam, a technical term in Psalm titles, meaning unknown (Psalms 16:1; Psalms 60:1; Psalms 56:1; Psalms 57:1; Psalms 58:1)

Pronunciation: mik-tawm' · Hebrew/Aramaic (Old Testament) · H4387

Same root

כָּתַםkâtham · H3799properly, to carve or engrave, i.e. (by implication) to inscribe indelibly

Where it appears

Appears 6 times in the Bible.

Psalms 16:0
Psalms 56:0
Psalms 57:0
Psalms 58:0
Psalms 59:0
Psalms 60:0

Source: Brown, Driver and Briggs, Hebrew and English Lexicon of the Old Testament (1906), public domain; markup by unfoldingWord, CC BY (github.com/unfoldingWord/Brown-Driver-Briggs-Enhanced).