Mid-market
The price halfway between the displayed bid and ask. A midpoint trade gives less directional evidence than a trade at either side of the spread.
The mid-market price is the average of the current bid and ask. Many limit orders and negotiated trades fill at or near it, because neither side pays the full spread.
For flow analysis, a print near the midpoint says little about who initiated the trade, so scanners often classify it as neutral or leave its direction unassigned. The midpoint is also a common reference for valuing a position, although the price available in a trade can differ from it, especially when the spread is wide or the contract trades rarely.
Illustrative example (hypothetical numbers, not a real trade): a call is quoted $4.80 bid and $5.20 ask, so the midpoint is $5.00. A print at $5.00 sits exactly between buyer and seller, while a print at $5.20 would be ask-side.