With reference to GUI widgets, the term metawidget has been adopted for different purposes. It has been used to describe a 'widget of widgets', a 'widget about widgets' and also a 'widget for metadata'.
A widget that is composed of other (usually more primitive) widgets.
This is using the term meta in its epistemological sense, whereby it means about (its own category). For example, a Spinner widget could be implemented as a metawidget consisting of a Text box and two Buttons. An alternative term would be 'compound widget'.
Metawidget is an Open Source project that targets multiple widget toolkits. It mines an application's existing architecture and creates widgets native to its existing widget toolkit.
mkWidgets is an Open Source project written for the Tcl/Tk framework. It provides a method for defining metawidgets, and includes a collection of pre-built ones.
A widget that chooses to be one of a range of possible widgets depending on requirements.
This is using the term meta in its slightly different interpretation, whereby it means on (exactly its own category). For example, a widget may choose to represent itself to the user as an image, as sound, or as various combinations and/or sequences of the two depending on the capabilities of the device
A widget that captures or displays metadata.
FitNesse is a web server, a wiki, and a software testing tool. It has a class fitnesse.wikitext.widgets.MetaWidget for storing and editing metadata
TurboGears is a Python web application framework. It has a class turbogears::widgets::meta::MetaWidget for storing and editing metadata