Dictionary:

umbel

  (ŭm'bəl)

A flat-topped or rounded flower cluster in which the individual flower stalks arise from about the same point, as in the geranium, milkweed, onion, and chive.

[New Latin umbella, from Latin, parasol, diminutive of umbra, shadow.]

1. A flower cluster in which the individual flower stalks emerge from the same point on the stem, like the ribs of an umbrella.
2. A member of the family Umbelliferae (formerly called Apiaceae), or carrot family. Carrots, parsley, and dill are examples.

The noun has one meaning:

Meaning #1: 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

Umbels on Wild Carrot Daucus carota (Apiaceae)

An umbel is an inflorescence which consists of a number of short flower stalks (called pedicels) which are equal in length and spread from a common point, somewhat like umbrella ribs.

An umbel on Fatsia japonica (Araliaceae)

Umbels are a characteristic of plants such as carrot, parsley, dill, and fennel in the family Apiaceae, and ivy, aralia and fatsia in the family Araliaceae.

A compressed cyme is called umbelliform if it resembles an umbel.

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