noun

• A signal fire to notify of the approach of an enemy, or to give any notice, commonly of warning.
• A signal or conspicuous mark erected on an eminence near the shore, or moored in shoal water, as a guide to mariners.
• A high hill or other easily distinguishable object near the shore which can serve as guidance for seafarers.
• That which gives notice of danger, or keeps people on the correct path.
• An electronic device that broadcasts a signal to nearby portable devices, enabling smartphones etc. to perform actions when in physical proximity to the beacon.