Cluster Stitch

Intermediate Textured

Several unfinished stitches worked into the same space and joined together at the top into one raised bump.

Work to the stitch or space where the pattern calls for a cluster.
Yarn over, insert your hook into the stitch, yarn over and draw up a loop, then yarn over and draw through the first two loops only — 2 loops remain on your hook. This is one unfinished double crochet.
Repeat the previous step in the same stitch, or the next few stitches as your pattern specifies, two to four more times, leaving each unfinished stitch's last loop on the hook.
Once all the unfinished stitches are on your hook, yarn over and draw through all the remaining loops at once, closing the cluster into a single stitch at the top.

Clusters are built from several unfinished stitches closed together at the top — the same closing move used in bobble and popcorn stitch, just with fewer, taller legs.
Working clusters into the same stitch pulls the fabric in around that point, which is what gives cluster stitch its characteristic raised, gathered texture.
Keep your final yarn-over pull snug but not tight — closing a cluster too tightly makes it hard to work into on the following row.