Of sand, the ground, etc.: mobile, shifting, readily yielding to pressure. Chiefly in quicksand, n. Cf. quick clay n. at compounds 1b.

Of ground: that yields underfoot; full of quags; boggy; soft. Also of a stream: flowing through boggy soil.

= quaggy, adj. (in either sense). Now rare.

Consisting of or resembling a quagmire; sunk in a quagmire. Also figurative.