As a software developer I fight "Smells" as much as I can.
I love the term, it's very plastic, intuitive and easily adopted by most of the people. I use it with different meanings: design smells (code that screams for refactoring), software aging smells (deprecated, dead code), testability smells (untestable code, low code coverages), etc..
I first encountered the term in Refactoring - Improving the Design of Existing Code, and I adopted it instantly. When I use the word, I'm understood immediately!
One of these days, I had a discussion with a colleague of mine and we laughed together about a new meaning of the word, or if you wish a new metaphor, old software projects as Smelly Rooms:
As you stay longer in a smelly room, you adapt, you find the air there more breathable. You even start to think there's nothing smelly with the air you bread. Same can happen when living too long in a Smelly Project, you can get used to the design smells, software aging smells, etc. It's possible you'll even start to think you're working on a state of the art piece of software!
The cure for this disease in both cases, smelly rooms and smelly projects: the door. Use the door to see the hallway, to enter other rooms, you'll just know you need to open some windows. Enter doors towards external projects (read books and articles, discover tools, have a look on an open source project, attach sources to external libraries you use and explore them, etc), and you'll just know you need to perform some cleanup to your old project.