functions.php

<?php
/* Filter to the post_class. */
add_filter( 'post_class', 'remove_class' );

/**
 * Remove class from post_class() function.
 */
function remove_class( $classes ) {
	$classes = array_diff( $classes, array( 'hentry' ) ); // seperate with commas for more than one class.
	return $classes;
}
?>