Holdfast

Part of speech: noun (n.)

1. Something used to secure and hold in place something else, as a long fiat-headed nail, a catch a hook, a clinch, a clamp, etc.; hence, a support. "His holdfast was gone." Bp. Montagu.

2. A conical or branching body, by which a seaweed is attached to its support, and differing from a root in that it is not specially absorbent of moisture.