Verb (5-dan, く, transitive)
1.  to open;  to undo;  to unseal;  to unpack
2.  to bloom;  to unfold;  to spread out
3.  to open (for business, e.g. in the morning)
4.  to be wide (gap, etc.);  to widen
Verb (5-dan, く, transitive)
5.  to hold (meeting, party, etc.);  to give;  to open
6.  to found (nation, dynasty, sect, etc.);  to open (a new business);  to set up;  to establish;  to start
7.  to open (ports, borders, etc.)
8.  to open (an account)
9.  to open up (new land, path, etc.);  to clear;  to develop
10.  to open (a file, etc.)
11.  to extract (root);  to reduce (equation)
12.  to cut open (fish)
as 魚を開く
13.  to change (kanji into hiragana)
Verb (5-dan, く, intransitive)
14.  to flare (e.g. skirt)
15.  to slacken (into a poor posture)
as 体が開く, 肩が開く, etc.