thicken

Short definition from Wiktionary

Verb

1. 1
   To make thicker (in the sense of wider).
2. 2
   To make thicker (in the sense of more viscous).
3. 3
   To become thicker (in the sense of wider).
4. 4
   To become thicker (in the sense of more viscous).
5. 5
   To strengthen; to confirm.
6. 6
   To make more frequent.
7. 7
   To make more detailed or comprehensive.