Qinah is a poetic metre used in various places in the Hebrew Bible (the Christian Old Testament) and most notably in the Book of Lamentations.
The metre describes pairs of unbalanced lines, the first having three stresses, the second having two. For example 2:7 nab is three such line-pairs:
In the Bible this 3:2 stress pattern is found in some (not all) dirges, for which the Hebrew technical term is qinah. Consequently, this term also became applied to the metre itself. The metre is often described as a "limping beat", sometimes characterised as "three beats of weeping followed by two beats of sobs".
Rather than Budde's late nineteenth century description of this as "metre", many scholars nowadays prefer the description of "rhythm", which is less tied to syllable counting.
Not all biblical dirges or laments are written in this metre, such as David's lament over Saul and Jonathan in 1:17-27 nab. And other, brighter passages do use this metre such as 1:9-11 nab and the hopeful 40:9-11 nab.