alter UK /ˈɒl.tə/US /ˈɔl.təɹ/verb 5noun 1forms 6 verb5 •To change the form or structure of.No power in Venice can alter a decree. — 1596 •To become different.[…] Passing the song of the hermit bird and the tallying song of my soul, / Victorious song, death’s outlet song, yet varying ever-altering song, […] — 1865 •To tailor clothes to make them fit. •To affect mentally, as by psychotropic drugs or illness.We don't know if he was altered on alcohol or drugs or anything […] — 2016 •To castrate, neuter or spay (a dog or other animal). noun1 •One of the personalities, identities, or selves in a person with dissociative identity disorder or another form of multiplicity.While the second goal would be best met if each alter were coconscious, the defendant should be satisfied if at least one competent alter is present to hear what transpires. — 2000 formsalter'd · altered · altering · altereth · alters · alterest