What is the meaning of Holdfast?

Something to or by which an object can be securely fastened.

A root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, stalked crinoids, benthic cnidarians, and sponges, to the substrate.

Actinomycosis.

The aspect of a character that experiences destructive temptation.

Source: wiktionary.org