In business, a white knight refers to a potential acquirer (i.e., a firm that wishes to acquire ownership of another firm). The intention of the acquisition is to circumvent the hostile takeover of the target firm by a third firm, which is perceived to be less favorable.
For example, if Company T (target) is going to be acquired by Company H (hostile firm), but Company A (acquirer) can acquire ownership of Company T, then Company A would be acting as the white knight.
See also