Robert Wilson appears to be the ideal Hemingway male - masculine, strong, unemotional, coveted by women, and, above all, fearless. Yet notice as the story progresses that he is not really all we are led to believe. Remember, he is hired by Francis and his wife, so he is really at their service. Plus, there is that quote about him traveling with the rich and fast type of high society people, whose wives don\'t feel like they have gotten their money\'s worth until they have slept with the great white hunter. So even though Wilson appears to be the ideal Hemingway male, he also has a very pathetic side to him as well.
Well, no character has just a single characteristic, but if I had to name just one, in Hemingway's world, Wilson is masculine. He is a hunter, he's confident, he's calm, he's assertive, and all of those describe him (though technically "hunter" is not an adjective).
If you'd accepted other terms based on his emotional tone, he is cool, judgmental, and opportunistic. Finally, he is flexible/adaptable: he can change to meet the needs of the situation, which Macomber cannot.