How to search for multiple synonyms?
To avoid problems with cycles in your graph, I would suggest that you re-design your structure to:
CREATE TABLE products
( product_id ... NOT NULL PRIMARY KEY
, ...
);

CREATE TABLE synonym_groups
( synonym_group_id ... NOT NULL PRIMARY KEY
, ...
);

CREATE TABLE synonym_group_products
( synonym_group_id ... NOT NULL
, product_id NOT NULL PRIMARY KEY  -- A product belongs to exactly one group 
,     CONSTRAINT ... 
      FOREIGN KEY (synonym_group_id)
          REFERENCES synonym_groups (synonym_group_id)
,     CONSTRAINT ... 
      FOREIGN KEY (product_id)
          REFERENCES products (product_id)
);

I created a Fiddle, I just used integer for keys since I don't know what identifies your entities. To get the synonyms of chiptune:
select p2.*
FROM products p1
JOIN synonym_group_products sgp1
    ON p1.product_id = sgp1.product_id
JOIN synonym_group_products sgp2
    ON sgp1.synonym_group_id = sgp2.synonym_group_id
JOIN products p2
    ON sgp2.product_id = p2.product_id
WHERE p1.product_name = 'chiptune'
  AND p1.product_id &lt;&gt; p2.product_id;