Three contexts: (1) industry/manufacturing - non-standard shapes (异型钢材 specialty steel, 异型砖 shaped bricks); (2) medicine - atypical cells, often a precancer warning; (3) film - Ridley Scott's Alien is rendered 《异形》 in mainland Chinese (note 形 not 型, but 异型 also appears in older translations).
mistakes
Don't mix up with 异性 (yìxìng, "opposite sex") - same pinyin, totally different meaning. The 型/形 distinction here matters too: 型 = type/model, 形 = shape/form. The Alien franchise uses 异形 (alien shape); industrial parts use 异型 (irregular type).
