thicken

Etymology

From Middle English thickenen, thikkenen, perhaps from Old Norse þykkna (“to thicken”); equivalent to thick + -en. Cognate with Swedish tjockna (“to thicken”), Icelandic þykkna (“to thicken”).

verb

1. (transitive) To make thicker (in the sense of wider).
2. (transitive) To make thicker (in the sense of more viscous).
   to thicken a sauce
3. (intransitive) To become thicker (in the sense of wider).
   As we age, the major arteries of our bodies frequently become thickened with plaque, a fatty material with an oatmeal-like consistency that builds up along the inner lining of blood vessels. The reason plaque forms isn’t entirely known, but it seems to be related to high levels of cholesterol inducing an inflammatory response, which can also attract and trap more cellular debris over time. 2013 July-August, Stephen P. Lownie, David M. Pelz, “Stents to Prevent Stroke”, in American Scientist
4. (intransitive) To become thicker (in the sense of more viscous).
5. (transitive) To strengthen; to confirm.
6. (transitive) To make more frequent.
   to thicken blows