WordPress at a glance
action is not described

admin_head action-hook . WP 1.0

This action is documented in wp-admin/admin-header.php

Usage

add_action( 'admin_head', 'action_function_name_4396' );
function action_function_name_4396(){
	// action...
}

Where the hook is called

iframe_header()
admin_head
wp_iframe()
admin_head
wp-admin/includes/template.php 2058
do_action( 'admin_head' );
wp-admin/includes/media.php 571
do_action( 'admin_head' );
wp-admin/admin-header.php 147
do_action( 'admin_head' );

Where in WP core the hook is used WordPress

wp-admin/includes/template.php 44
add_action( 'admin_head', 'export_add_js' );
wp-admin/includes/template.php 44
add_action( 'admin_head', 'wp_admin_canonical_url' );
wp-admin/includes/template.php 45
add_action( 'admin_head', 'wp_color_scheme_settings' );
wp-admin/includes/template.php 46
add_action( 'admin_head', 'wp_site_icon' );
wp-admin/includes/template.php 47
add_action( 'admin_head', 'wp_admin_viewport_meta' );
wp-admin/includes/template.php 43
add_action( 'admin_head', 'network_settings_add_js' );
wp-admin/includes/template.php 24
add_action( 'admin_head', 'options_general_add_js' );
wp-admin/includes/template.php 19
add_action( 'admin_head', 'options_reading_add_js' );
wp-admin/includes/template.php 29
remove_action( 'admin_head', 'wp_admin_canonical_url' );
wp-admin/includes/template.php 264
add_action( 'admin_head', 'delete_users_add_js' );
wp-admin/includes/template.php 56
add_action( 'admin_head', 'wp_admin_bar_header' );
wp-admin/includes/template.php 4635
add_action( 'admin_head', '_thickbox_path_admin_subfolder' );