For the physical object:
* Mooring: This is the most common synonym for the physical object that secures a boat.
* Holdfast: This is a more technical term used in nautical contexts.
* Grapple: This is a synonym for a type of anchor with multiple hooks.
For the metaphorical meaning:
* Foundation: This refers to the anchor's role in providing stability.
* Support: This signifies the anchor's role in giving strength and security.
* Center: This emphasizes the anchor's position as the main point of reference.
* Stability: This describes the state that the anchor creates.
* Security: This highlights the anchor's ability to provide safety and assurance.
* Backbone: This emphasizes the anchor's role as a crucial element in a system.
The best synonym for "anchor" depends on the specific context in which you are using it.