When things get stuck or clumped together, they agglutinate. In biology, red blood cells are said to agglutinate when they adhere to each other, forming a mass of cells.
There's glue at the heart of agglutinate — it comes from the Latin agglutinare, "fasten with glue." Microbiologists use this word to describe the behavior of cells and particles. Linguistics experts also use this verb: when words or sounds agglutinate, they are strung together to form more complex compound words. In English, one example is shamelessness, which agglutinates shame, less, and ness.