A "limb bud" refers to a small lump or bump that forms on the body of an embryo, which later develops into a limb, like an arm or a leg. It's like the starting point of where arms and legs begin to grow in a developing baby. Full definition
Your baby's neck is taking shape, along with little limb buds. (pregnancy-baby.com)
A key regulator protein controlling the balance of anterior and posterior fields of limb buds of tetrapods is Gli3. (sciencedaily.com)
«Key genetic event underlying fin - to - limb evolution: Study of catsharks reveals how alterations in the expression, function of certain genes in limb buds underlie evolution of fish fins to limbs.» (sciencedaily.com)