Longman Dictionary of Contemporary English
stretch mark
noun
EXAMPLES FROM CORPUS
▪ I make up my own recipe for stretch mark ointment and of course she was thrilled to have it.
Wiktionary
stretch mark
n. Any of a series of red, irregular stripes on the surface of the skin caused by rapid growth of the tissues lying just underneath. They usually appear as a result of pregnancy, puberty or obesity, but can also be caused by rapid muscle growth.
WordNet
stretch mark
n. a narrow band resulting from tension on the skin (as on abdominal skin after pregnancy)
Usage examples of "stretch mark".
It was ever a joy to look at Star but I tried to look at her freshly, for hints of autumn--outer corners of eyes, her hands, for tiny changes in skin--hell, not even a stretch mark, yet I knew she had a grandchild.