An underdog is a company (or brand or organization or division or group) who is...
Ranked number two or lower in their industry.
Uses ideas and action to outsmart vs. out-spend their competitors.
Be clear: simply being second, third or thirtieth in your market isn’t enough to make you an underdog. Nor is being a company who is smaller or “weaker.”
Most successful underdogs—even if they’re well behind the market leader in terms of size or sales—aren’t thought of that way at all. In fact, underdogs are often considered some of the world’s most successful companies. From Apple (who has less than a 4% share of the overall computer market) to Southwest Airlines, underdogs consistently are viewed as leaders in their industries despite not being in the number one position.
That’s because being an underdog is more about your frame of mind than your market position. Again for emphasis: being an underdog is more about your frame of mind than your market position.