add_action( 'cmb2_admin_init', 'yourprefix_register_taxonomy_metabox' );
 /**
  * Hook in and add a metabox to add fields to taxonomy terms
  */
 function yourprefix_register_taxonomy_metabox() {
 	$prefix = 'yourprefix_term_';

 	/**
 	 * Metabox to add fields to categories and tags
 	 */
 	$cmb_term = new_cmb2_box( array(
 		'id'               => $prefix . 'edit',
 		'title'            => esc_html__( 'Category Metabox', 'cmb2' ), // Doesn't output for term boxes
 		'object_types'     => array( 'term' ), // Tells CMB2 to use term_meta vs post_meta
 		'taxonomies'       => array( 'category', 'post_tag' ), // Tells CMB2 which taxonomies should have these fields
 		// 'new_term_section' => true, // Will display in the "Add New Category" section
 	) );

 	$cmb_term->add_field( array(
 		'name'     => esc_html__( 'Extra Info', 'cmb2' ),
 		'desc'     => esc_html__( 'field description (optional)', 'cmb2' ),
 		'id'       => $prefix . 'extra_info',
 		'type'     => 'title',
 		'on_front' => false,
 	) );

 	$cmb_term->add_field( array(
 		'name' => esc_html__( 'Term Image', 'cmb2' ),
 		'desc' => esc_html__( 'field description (optional)', 'cmb2' ),
 		'id'   => $prefix . 'avatar',
 		'type' => 'file',
 	) );

 	$cmb_term->add_field( array(
 		'name' => esc_html__( 'Arbitrary Term Field', 'cmb2' ),
 		'desc' => esc_html__( 'field description (optional)', 'cmb2' ),
 		'id'   => $prefix . 'term_text_field',
 		'type' => 'text',
 	) );

 }