Proxyholder

A person (individual) appointed to act on behalf of a company or other entity (such as a trust). He or she is authorized by power of attorney to make decisions or sign documents for that company or entity.

Example:

Company A holds shares in Company B. If Company A appoints a person as its proxyholder, that person will be able to act on behalf of Company A, for example to attend Company B's shareholders' meeting, vote, or sign contracts concerning Company A's shares in Company B.

So, in summary, a proxyholder represents a company or trust and can act on behalf of that entity, even if that entity is itself a shareholder in another corporation.