These words indicate the forcing of a sharp, pointed instrument into something by means of a driving or cutting action. Pierce may suggest merely the cutting of any opening into something, though more often it is used to indicate the cutting of a hole entirely through a thin layer to its other side: a screen pierced to let light through; piercing a balloon; a hat pierced by a hatpin; instruments with which to pierce ears. By implication, the opening through the layer is made by a sharp, thin object such as a needle or lance. Stab , by contrast, suggests that something is merely cut into, not pierced ; furthermore, stab suggests the use of a bladed instrument such a sword or knife rather than something needlelike, as with pierce : stabbing the man with his dagger. Prick is more nearly comparable to pierce , but specifically may suggest a light, glancing thrust of a needlelike instrument to make a small opening in or through a thin layer: pricking the blister with a heated needle; thorns that pricked his skin as he ran.

Penetrate is more formal and more general than the foregoing. It may suggest the partial or complete passage made by any sort of instrument: measuring the depth to which the bullet had penetrated the flesh; a façade of marble penetrated by three rows of windows. The word may also suggest the achieving of any sort of entrance into or through something, whether along an existing passageway, through a discontinuous mass, or through a permeable membrane; in these cases, the act may by implication be difficult but it may be achieved without altering or actually piercing the medium itself: brave explorers who first penetrated the jungles of Africa; light that penetrated the dusty windows. Probe suggests a deliberate, cautious or exploratory attempt to penetrate something; the passage may already exist or may be made by the act of proving: carefully probing the cavity with a toothpick; two men sent in to probe the tunnels for possible survivors.