When you attack with a weapon whose mastery property you can use, you can replace that property with the Push, Sap, or Slow property for that attack.
Tactical Master
Raw data
{
"name": "Tactical Master",
"page": 92,
"level": 9,
"srd52": true,
"__prop": "classFeature",
"source": "XPHB",
"entries": [
"When you attack with a weapon whose mastery property you can use, you can replace that property with the {@itemMastery Push|XPHB}, {@itemMastery Sap|XPHB}, or {@itemMastery Slow|XPHB} property for that attack."
],
"className": "Fighter",
"classSource": "XPHB",
"basicRules2024": true
}