The term 'metaredundant' means redundant on a redundant relation.
So, in a tristratal system, such as that of meaning–wording–sounding, the term metaredundancy refers to meaning being redundant on the redundant relation between wording and sounding.
Note that 'metaredundant' does not refer to the relation between any given pair of strata, such as meaning and wording, or wording and sounding.