This work describes a new method of designing an anti-jam communications system. The key insight is that many of the concepts learned from interference alignment (IA) in multiple antenna (MIMO) systems can be applied to the field of antijam and robust communications in the presence of intentional jammers. It provides a new fundamental technique of hiding a signal, similar to the mature techniques of frequency hopping or direct sequence spread spectrum. This paper considers a realistic jamming scenario and provides a precoding technique that allows a pair of two-antenna transceivers to communicate while being jammed by a malicious single-antenna node. The precoder uses a small amount of channel information to shape the signal to appear orthogonal to the jammer at the intended receiver. The novelty introduced in this paper is both the application of interference alignment (IA) to anti-jamming communications and a specific method that allows these IA techniques to be practically employed.