baby jumper

from The Century Dictionary.

• noun A basket or sling in which a small child may be fastened, having an adjustable elastic cord which permits a dancing motion when the child's feet touch the floor.

from the GNU version of the Collaborative International Dictionary of English.

• A hoop suspended by an elastic strap, in which a young child may be held secure while amusing itself by jumping on the floor.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A hoop suspended by an elastic strap, in which a young child may be held secure while amusing itself by jumping on the floor.