Technically, an acrostic is a literary pattern in which the first letter of each unit forms a word. In the Psalms it refers to poems where the first letter of each stanza follows the course of the Hebrew alphabet.

Psa 119 is most famous. It is a perfect acrostic with eight lines per letter. Psalm 111 and 112 are also perfect acrostics with two letters per verse except for three each in vv Interestingly, "Praise the Lord" does not count and may therefore be a title.

Psalm 25 & 35 are nearly perfect acrostics, missing only waw and qoph (though there are two resh ) and adding a pe at the end.

Psalm 37, lacks only an ayin but has a tzade in its place, which looks very similar. The final taw is preceded by a consecutive waw. Some letters precede two verses others just one. Psalm 145is a perfect acrostic except that it is missing the nun which has resurfaced in the DSS and is now included in the NIV, NRSV, ESV. It is in the LXX but not in the Targum of the Psalms.

Psalm 9-10 may have been a single acrostic at every other verse. However, Psa 9 has only "a, b, c" then skips two letters, has a waw and then skips to kaph. Psalm 10 starts with lamed (for six verses), then skips to ayin and samech, then jumps to shin. This is far too inconsistent.