WordPress at a glance
function is not described

Automattic\WooCommerce\Admin

FeaturePlugin::define() protected WC 1.0

Define constant if not already set.

{} It's a method of the class: FeaturePlugin{}

No Hooks.

Return

null. Nothing.

Usage

// protected - for code of main (parent) or child class
$result = $this->define( $name, $value );
$name(string) (required)
Constant name.
$value(string|true|false) (required)
Constant value.

Code of FeaturePlugin::define() WC 5.3.0

<?php
protected function define( $name, $value ) {
	if ( ! defined( $name ) ) {
		define( $name, $value );
	}
}