-Keyword @code{:weakness} can be @code{nil} (default), @code{t},
-@code{key} or @code{value}.
-
-A weak hash table is one whose pointers do not count as GC referents:
-for any key-value pair in the hash table, if the only remaining pointer
-to either the key or the value is in a weak hash table, then the pair
-will be removed from the hash table, and the key and value collected.
-A non-weak hash table (or any other pointer) would prevent the object
-from being collected.
+Non-standard keyword @code{:weakness} can be @code{nil} (default),
+@code{t}, @code{key-and-value}, @code{key}, @code{value} or
+@code{key-or-value}. @code{t} is an alias for @code{key-and-value}.
+
+A key-and-value-weak hash table, also known as a fully-weak or simply
+as a weak hash table, is one whose pointers do not count as GC
+referents: for any key-value pair in the hash table, if the only
+remaining pointer to either the key or the value is in a weak hash
+table, then the pair will be removed from the hash table, and the key
+and value collected. A non-weak hash table (or any other pointer)
+would prevent the object from being collected.