'To suck in' definitions:

Definition of 'To suck in'

From: GCIDE

Suck \Suck\ (s[u^]k), v. t. [imp. & p. p. Sucked (s[u^]kt); p. pr. & vb. n. Sucking.] [OE. suken, souken, AS. s[=u]can, s[=u]gan; akin to D. zuigen, G. saugen, OHG. s[=u]gan, Icel. s[=u]ga, sj[=u]ga, Sw. suga, Dan. suge, L. sugere. Cf. Honeysuckle, Soak, Succulent, Suction.]
1. To draw, as a liquid, by the action of the mouth and tongue, which tends to produce a vacuum, and causes the liquid to rush in by atmospheric pressure; to draw, or apply force to, by exhausting the air. [1913 Webster]
2. To draw liquid from by the action of the mouth; as, to suck an orange; specifically, to draw milk from (the mother, the breast, etc.) with the mouth; as, the young of an animal sucks the mother, or dam; an infant sucks the breast. [1913 Webster]
3. To draw in, or imbibe, by any process resembles sucking; to inhale; to absorb; as, to suck in air; the roots of plants suck water from the ground. [1913 Webster]
4. To draw or drain. [1913 Webster]
Old ocean, sucked through the porous globe. --Thomson. [1913 Webster]
5. To draw in, as a whirlpool; to swallow up. [1913 Webster]
As waters are by whirlpools sucked and drawn. --Dryden. [1913 Webster]
To suck in, to draw into the mouth; to imbibe; to absorb.
To suck out, to draw out with the mouth; to empty by suction.
To suck up, to draw into the mouth; to draw up by suction or absorption. [1913 Webster]