In functions.php

add_action( ‘pre_get_posts’, ‘query_posts_order_price’);

function query_posts_order_price($query) {

if ( $query->is_search ) {

$query->set( ‘tax_query’, array(
array(

‘taxonomy’ => ‘product_cat’,  // taxonomy

‘field’ => ‘slug’,

‘terms’ => array( ‘cat1’, ‘cat2’ ), // categories to be removed

‘operator’ => ‘NOT IN’   // Operation

)));

}
}