Holdfast

Origin

hold + fast

Full definition of holdfast

Noun

1. Something to or by which an object can be securely fastened.
2. (zoology) A root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, stalked crinoids, benthic cnidarians, and sponges, to the substrate.
3. (archaic, medicine) Actinomycosis.