A Choppy Market, or one with a lot of “chop”, is slang for a range-bound market.
The market swings up and down a lot, with lots of volatility and no apparent trend.
Choppy markets occur when the fight between buyers (bulls) and sellers (bears) is roughly even.
Neither group is winning outright.
Being a trend trader or utilizing a trend-based trading strategy is generally less profitable when the market is choppy and no clear trend exists.
See Range-bound market for more info.