Ultra vires literally means beyond the powers. It is a rule of capacity.
The so-called ultra-vires in the wider sense is nothing but an abuse of powers of the company its officers often described as excesses of directors or transactions ultravires the directors.
E.g. borrowing for ultra vires purposes
A transaction ultra vires in the wider sense is ultra vires the company. However, it is voidable at the option of the company.
Such a transaction may be ratified members in general meeting whereupon it ceases to be voidable.
A transaction ultra vires in the wider sense is enforceable, if the other party was unaware of the abuse of power. As was the case in David Payne and Co. Ltd. It is unenforceable if the other party had notice of the abuse of power. As was the case in re Introductions Ltd.