Wiktionary
lambdoid suture
n. (context anatomy English) A dense, fibrous connective tissue joint on the posterior aspect of the skull that connects the parietal and temporal bone with the occipital bone.
Wikipedia
Lambdoid suture
The lambdoid suture (or lambdoidal suture) is a dense, fibrous connective tissue joint on the posterior aspect of the skull that connects the parietal bones with the occipital bone. It is continuous with the occipitomastoid suture.
Its name comes from its lambda-like shape.