Positive Gamma Environment
A positive Gamma environment generally refers to a market regime in which estimated dealer positioning implies positive aggregate Gamma under the model being used.
Why it matters to you
If dealers are effectively long Gamma, their Delta hedging activity may tend to involve: selling some underlying exposure as prices rise, and buying some underlying exposure as prices fall. All else equal, this type of hedging flow can have a dampening effect on short term price movement. But it is only one influence among many.