The word "crusty" can be used to describe a variety of things that have a hard and rough outer layer, such as bread crust or a scab. However, if you're looking for synonyms to use in your writing, there are many other words that might be more suitable for your specific context. Some possible alternatives to "crusty" include rough, rugged, bumpy, pebbled, textured, or scaly. For descriptions that are more sensory or evocative, you could consider using words like gnarled, knobbly, weathered, time-worn, flaky, or craggy. Whether you're writing about food, skin, or landscapes, there's sure to be a synonym that fits your needs perfectly!