<?php
$search_query = get_search_query();

$term = get_term_by( 'name', $search_query, 'category' );
if ( !empty( $terms ) && !is_wp_error( $terms ) ){
    echo "<ul>";
    foreach ( $terms as $term ) {
    echo "<li>" . $term->name . "</li>";
    }
    echo "</ul>";
}
;?>