holdfast

/HH OW1 L F AE0 S T/
noun
  1. 1

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

  2. 2

    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. 3

    Actinomycosis.

Source: https://en.wiktionary.org/wiki/holdfast