sequestration āļāļ·āļāļāļ°āđāļĢ sequestration āļāļ·āļāļāļ°āđāļĢ The act of sequestering; segregation.Law Seizure of property.Law A writ authorizing seizure of property.Chemistry The inhibition or prevention of normal ion behavior by combination with added materials, especially the prevention of metallic ion precipitation from solution by formation of a coordination compound with a phosphate.