to accumulate;  to gather;  to concentrate
To gather up one's mind
I prefer to do my work as (and when) it comes rather than letting it pile up
to corner;  to drive somebody into a corner
To be driven into a corner
to cram;  to stuff
to flock;  to huddle
to herd (animals or people)
to mix;  to merge;  to fuse
To fuse two schools (into one)
To quicken one's steps
To press somebody with uninterrupted questions
To summon up all one's strength