gettext-pmpro-buddypress.php

<?php
/**
 * Change the text for PMPro BuddyPress using the gettext filter.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

function my_pmpro_custom_text_strings_with_gettext( $translated_text, $original_text, $domain ) {
	switch ( $domain ) {
		case 'pmpro_buddypress':
			switch ( $original_text ) {
				case 'Membership':
					$translated_text = 'Your translation here';
					break;
			}
			break;
	}

	return $translated_text;
}
add_filter( 'gettext', 'my_pmpro_custom_text_strings_with_gettext', 10, 3 );