umbel

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A flat-topped or rounded flower cluster in which the individual flower stalks arise from about the same point, characteristic of plants in the parsley family, such as Queen Anne's lace.

from The Century Dictionary.

• noun In the spicular elements of the hexactinellid sponges, a straight shaft or rhabd with rays at one end grouped together in the form of an umbel.
• noun An inflorescence consisting of a number of flower-stalks or pedicels, nearly equal in length, spreading from a common center, their summits forming a level, convex, or even globose surface, more rarely a concave one, as in the carrot. See cuts under inflorescence, Thapsia, and Œnanthe.
• noun In zoology, an umbelliform tuft, cluster, or group of parts, as of polypites borne upon a polypidom. See cut under Umbellularia.

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

• noun (Bot.) A kind of flower cluster in which the flower stalks radiate from a common point, as in the carrot and milkweed. It is simple or compound; in the latter case, each peduncle bears another little umbel, called umbellet, or umbellule.

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

• noun botany A flat-topped or rounded flower-cluster (= inflorescence) in which the individual flower stalks arise from the same point, the youngest flowers being at the centre.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun flat-topped or rounded inflorescence characteristic of the family Umbelliferae in which the individual flower stalks arise from about the same point; youngest flowers are at the center