To tamp something is to press it down by tapping or pushing on it — not one big shove, but several small firm hits, until the stuff underneath is packed tight and even. You tamp earth around a new tree, tamp gravel into a hole in the road, tamp tobacco into a pipe. Coffee people use it constantly: you tamp the ground coffee flat in the basket before the machine runs water through it, and the metal tool for doing it is a tamper. The point of tamping is always the same — getting rid of air and loose space so what is left is dense and level. That is why it needs the tapping. Pressing once leaves soft spots. There is also tamp down, which is the same action with the meaning pushed sideways onto feelings and situations: "tamp down your excitement", "the government tried to tamp down the rumours". It means press something so it stays small and quiet. This use is common in news writing. A warning about spelling: tamp and tamper look related but the ordinary verb tamper (with) means to touch and mess with something you should not — a different word with a different story. See tamper-evident.

夯實、壓實、（咖啡）填壓。台灣咖啡圈直接講「填壓」，工具叫「填壓器 / tamper」；工地上把土壓實叫「夯實」。