WordPress at a glance
filter is not described

default_excerpt filter-hook . WP 1.5.0

Filters the default post excerpt initially used in the "Write Post" form.

Usage

add_filter( 'default_excerpt', 'filter_function_name_4083', 10, 2 );
function filter_function_name_4083( $post_excerpt, $post ){
	// filter...

	return $post_excerpt;
}
$post_excerpt(string)
Default post excerpt.
$post(WP_Post)
Post object.

Where the hook is called

get_default_post_to_edit()
wp-admin/includes/post.php 662
$post->post_excerpt = (string) apply_filters( 'default_excerpt', $post_excerpt, $post );

Where the hook is used (in WP core)

Does not used.