I've seen people wearing t-shirts have the Kanji for Kaizen on them. If you're going to wear the shirt you should know what you're saying. According to the Googles, Kaizen translates to "Improvement". That's simple enough, and a worthy goal, but when you connect the term to Toyota it brings in an additional level of meaning, the Toyota Production System, or The Toyota Way. It's about culture and culture change. It's about expectations. It's about empowerment and obligations. At Toyota it was embodied by the Andon cord and this story:
When asked if they intended to give workers on the assembly line the power to stop production the answer was "No, we intend to give them the obligation to stop it whenever they find a problem."