Dictionary Definitions of the Word "Sovereign"

Collins English Dictionary gives:--

1. Noun.
   A person exercising supreme authority, especially a monarch.
2. Noun.
   A former English gold coin worth one pound sterling.
3. Adjective.
   Supreme in rank or authority;
   a sovereign lord.
4. Adjective.
   Excellent or outstanding;
   a sovereign remedy.
5. Adjective.
   Of, relating to, or characteristic of a sovereign.
6. Adjective.
   Independent of outside authority;
   a sovereign state.

Webster's International Encyclopedia gives:-

• Sovereignty
  Ultimate political power in a state. In political theory, debates on sovereignty center on the role of the sovereign and on the nature of supreme power - by what rights, and by whom, it should be wielded. A sovereign state is one that is independent of control by other states. The modern theory of sovereignty was developed by Jean Bodin and Thomas Hobbes (1756), who studied the sovereignty of monarchs. The extension of their thought has been applied to the modern state.

Gold One Pound Coin
Although a sovereign is a gold one pound coin, a gold pound coin is not necessarily a sovereign.
A pound coin struck in gold was issued as part of the gold proof set issued for the Golden Jubilee in 2002. This is not a gold sovereign.