noun, noun which may take the genitive case particle 'no'
irregular shape; irregular form
Describes something that is not regular in shape or form; often used in technical or descriptive contexts.
この土地は不整形なので、建物の設計が難しい。
Because this land is irregularly shaped, designing a building is difficult.
不整形な結晶が顕微鏡で観察された。
Irregularly shaped crystals were observed under the microscope.
不規則 means 'irregular' in the sense of not following a rule or pattern (e.g., irregular heartbeat), while 不整形 specifically refers to irregularity in physical shape or form.
Compound of 不 (fu-, 'not') + 整形 (seikei, 'shaping, form'). The spelling 不正形 uses 正 (sei, 'correct') instead of 整 (sei, 'arrange'), but the meaning is essentially the same.