WordPress at a glance
action is not described

transition_comment_status action-hook . WP 2.7.0

Fires when the comment status is in transition.

Usage

add_action( 'transition_comment_status', 'action_function_name_1800', 10, 3 );
function action_function_name_1800( $new_status, $old_status, $comment ){
	// action...
}
$new_status(int/string)
The new comment status.
$old_status(int/string)
The old comment status.
$comment(object)
The comment data.

Where the hook is called

wp_transition_comment_status()
transition_comment_status
wp-includes/comment.php 1615
do_action( 'transition_comment_status', $new_status, $old_status, $comment );

Where the hook is used (in WP core)

wp-includes/default-filters.php 252
add_action( 'transition_comment_status', '_clear_modified_cache_on_transition_comment_status', 10, 2 );