The phrase "length jeans" refers to a type of pants that fit well in terms of their length, usually falling at the right spot on a person's legs. Full definition
For a whimsical look, how about a slim fit ankle length jeans with a pink blouse and wedges! (myntra.com)
You'd be surprised how warm over the knee boots are, even when you don't have full length jeans with them. (charmedbycamille.com)
5 - pocket ankle - length jeans in washed stretch denim with hard - worn details, a regular waist, zip fly with a button and skinny legs. (www2.hm.com)