A "flexible spatula" refers to a cooking tool with a bendable and adaptable head. It is designed to easily slide under and lift food from a pan or dish without causing damage. Full definition
Add breadcrumbs and mustard, and cook 7 to 8 minutes, or until crumbs are deep golden, mixing, pressing, and separating with flexible spatula or back of fork. (vegetariantimes.com)
Give the dough a few last turns with a sturdy flexible spatula. (epicurious.com)
Divide potato mixture between hot pans and press down as firmly as possible to compact (a thin flexible spatula works well). (bonappetit.com)