What is "come to a head"

vb. 1 (context idiomatic English) To rapidly come to a turning point. 2 (context idiomatic English) To suddenly reveal that which has lain latent for a time. 3 (context idiomatic English) To suddenly make mature or perfected that which was inchoate or imperfectly formed. 4 (context medicine of an abscess English) To reach its final stage