The term 'OUTER COAT ON A SEED' can be summarized as the testa, which is a five-letter word. The testa is the outermost layer of a seed, also known as the seed coat. It is composed of two layers, the inner and outer integuments, and serves to protect the seed from physical damage, dehydration, and disease. The testa also helps to regulate the exchange of gases and water vapor between the seed and its environment.