There is still confusion over which terms people use to define different approaches to mobile and multi device websites. These are the terms I use.
Responsive design is defined as:
- Fluid grid used for layout
- Flexible images and media
- Use of media queries
This is the definition given in chapter one of "Responsive Web Design" by Ethan Marcotte who coined the term responsive design. Unless you are doing all of the above then I don't consider what you are doing as responsive design.
Adaptive layout refers to having more than one static width layout and switching between them using media queries. I much prefer the term Switchy McLayout but it doesn't sound very professional.
Serving content on one URL but using server side user agent detection to choose the layout you wish to serve is what I call layout switching - I don't know if there's a more widely used term for this.
Device Specific Websites
Device specific websites is the practice of having content served on different URLs and using server side user agent detection to direct devices to the site of your choosing.
Combining responsive design and server side techniques to modify content is known as RESS (REsponsive and Server Side).