thicken

American  

[thik-uhn] / ˈθɪk ən /

verb (used with or without object)

1. to make or become thick or thicker.

2. to make or grow more intense, profound, intricate, or complex.

   The plot thickens.

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thicken British  

/ ˈθɪkən /

verb

1. to make or become thick or thicker

   thicken the soup by adding flour

2. (intr) to become more involved

   the plot thickened

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Other Word Forms

• rethicken verb
• thickener noun
• unthicken verb (used with object)

Etymology

Origin of thicken

1375–1425; late Middle English thiknen < Old Norse thykkna. See thick, -en ¹

Explanation

To thicken is to become denser or to make something thicker. When you accidentally burn dinner, the smoke in the kitchen thickens. Time to get the fire extinguisher. There are two ways to thicken: to become thick or to make thick. Cooks often use flour or cornstarch to thicken sauces. And when you add flour to your brownie batter, you thicken it. An earlier, now obsolete meaning was "to crowd together." The phrase "the plot thickens" means that a situation is becoming more and more complicated or interesting.

Example Sentences

Let it come together for a few minutes, then blend part of it—just enough to thicken the base while leaving some beans intact.

From Salon • Apr. 3, 2026

At the same time, M proteins can also cause the blood to thicken and concentrate in urine, both of which can cause renal problems.

From Slate • Mar. 29, 2026

After months of painful practice, he learned a new style of playing – using his two good fingers to lay down chords, and adding vibrato to thicken the sound.

From BBC • Jul. 23, 2025

But these latest revelations only thicken the mystery: Who was Joan Didion?

From Los Angeles Times • Apr. 22, 2025

I heard August move across the porch, felt the air thicken as she stood behind me on the other side of the screen.

From "The Secret Life of Bees" by Sue Monk Kidd

Related Words

• clot
• condense
• congeal
• curdle
• swell