Definitions of ebb:

• noun:   the outward flow of the tide
• noun:   a gradual decline (in size or strength or power or number)
• verb:   fall away or decline

  Example: "The patient's strength ebbed away"

• verb:   hem in fish with stakes and nets so as to prevent them from going back into the sea with the ebb
• verb:   flow back or recede

  Example: "The tides ebbed at noon"