DimensionMetadata

Explains a dimension.

JSON representation 
{
  "apiName": string,
  "uiName": string,
  "description": string,
  "deprecatedApiNames": [
    string
  ],
  "customDefinition": boolean,
  "category": string
}
Fields
apiName

string

This dimension's name. Useable in Dimension's name. For example, eventName.
uiName

string

This dimension's name within the Google Analytics user interface. For example, Event name.
description

string

Description of how this dimension is used and calculated.
deprecatedApiNames[]

string

Still usable but deprecated names for this dimension. If populated, this dimension is available by either apiName or one of deprecatedApiNames for a period of time. After the deprecation period, the dimension will be available only by apiName.
customDefinition

boolean

True if the dimension is custom to this property. This includes user, event, & item scoped custom dimensions; to learn more about custom dimensions, see https://support.google.com/analytics/answer/14240153. This also include custom channel groups; to learn more about custom channel groups, see https://support.google.com/analytics/answer/13051316.
category

string

The display name of the category that this dimension belongs to. Similar dimensions and metrics are categorized together.