Straight-billed can be substituted for a variety of synonyms to convey the same meaning. Some of the words that can be used to replace straight-billed include long-billed, narrow-billed, slender-billed, thin-billed, and sharp-billed. All of these synonyms describe a bird's beak or bill that is straight and narrow. The term straight-billed is commonly used in bird watching circles to describe the characteristics of a particular species. However, using synonyms can add variety to your writing or conversation, making it more interesting and engaging for your audience. Choosing the right synonym for straight-billed depends on the context in which it is being used.