I work at a consulting shop and manage the web app development team. This is a question we struggle with as well. We've called it "custom business applications", "web applications", or simply "business applications".

Sometimes, it helps to focus less on the technology and more on the process of how you'd help your clients and the value you provide. Don't bother mentioning that you do "web" apps (as opposed to mobile or desktop). Describe the process and how you do what you do. That gets the conversation going, after which you can start discussing technology.