[kwawr-uh
m, kwohr-] 
| 1. | the number of members of a group or organization required to be present to transact business legally, usually a majority. |
| 2. | a particularly chosen group. |
| quo·rum (kwôr'əm, kwōr'-) n.
[Middle English, quorum of justices of the peace, from Latin quōrum, of whom (from the wording of a commission naming certain persons as members of a body), genitive pl. of quī, who; see kwo- in Indo-European roots.] |
The minimum number of members of a committee or legislative body who must be present before business can officially or legally be conducted. In the United States Congress, for example, either house must have a majority (218 in the House of Representatives, 51 in the Senate) to have a quorum.
Quorum
The minimum acceptable level of individuals with a vested interest in a company needed to make the proceedings of a meeting valid under the corporate charter.
Investopedia Commentary
This clause within a company's charter ensures that there is a sufficient representation of stockholders present at meetings before any changes can be made by the board.
See also: Annual General Meeting