Phil., physiol., med., alch.: (a) Change, transformation, transmutation; (b) change for the worse, deterioration; evel alteracioun; ill effect or result; (c) change for the better, amelioration……

Phil., physiol., med., alch., astrol. (a) To change, modify, transform; alteren to (sth.); (b) to change for the worse; affect adversely; deteriorate; (c) to change for the better; affect……

Physiol. To upset the proper balance of the humors or qualities. …

(a) To obstruct (a street, lane, passage, an entrance, etc.) with a physical barrier, block; close (a port), prevent access to; blockade (the sea), close to traffic; block (someone's way); also fig.……