pound, strike against, ram
摏 centers on forceful impact: pounding, striking against something, or ramming with a heavy blow.
摏 combines 扌 (hand) with 舂, which depicts a pestle pounding grain in a mortar. Together they suggest pounding or striking with the hand.
The hand radical 扌 beside 舂 (a pestle pounding grain in a mortar) shows a hand forcefully pounding or ramming something.
For ショウ, imagine a show of strength where someone pounds a giant mortar with a huge pestle: show -> ショウ, and the crowd watches the pounding.