A centrist is someone who has very moderate political views. Most centrists are against any big political shifts — either to the left or to the right.
Some politicians like to describe themselves as centrists because it makes them sound very reasonable and balanced. In reality, centrists are rare in politics, since people tend to have strong opinions about issues including taxes, the size of government, and inequality. Centrist comes from the French centriste, ultimately from the Latin centrum, "center."