A slang phrase referring to a tactic a hedge fund would use to try to mislead other funds that attempt to mimic its trades.
By making small trades but enthusiastically purporting these trades, a hedge fund will attempt to mislead other funds into thinking that these are its big trades and investments. The hedge fund doing the reverse desk is trying to minimize the amount that it is being copied by its competitors. If other hedge funds attempt to mimic a portfolio this increase in buying will result in increased prices, so by "doing the reverse desk" hedge funds are attempting also to get the most favorable prices for their trades. The results of this tactic stem from the fact that news about trading spreads very quickly, so by adding some noise into the communication process hedge funds can attempt to mislead other funds.