Verb (5-dan, む, transitive)
1.  to gulp down;  to swallow deeply
2.  to understand;  to take in;  to catch on to;  to learn;  to digest
3.  to engulf;  to swallow up
4.  to be filled with (people);  to be crowded
5.  to hold back from saying something;  to swallow (one's words)