Bloat is different from complete (or "feature-full"). Bloat means very long installation processes (Microsoft is the champion here), long startup times, slow software, huge memory requirements, crashes, etc.

When you install a typical, cheap consumer device under Windows (anything: a printer, a joystick, etc.) from the vendor's CD-ROM it usually installs megabytes of bullshit, including automatically-started craplets with shiny but useless owner-drawn GUIs, etc. This is bloat. When I plug-in some USB stuff in my OpenBSD laptop, the kernel spits a few lines on the console to tell it has recognized the device and that's all.

edit: the last releases of Acrobat Reader, huge, very slow and buggy are a very good example of bloat.