We don't have synonyms for blue slip yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are blue chip, blue lie and blue tulip.
(n) :
(US politics) In the Senate, the slip on which the senators from the state of residence of a federal judicial nominee give an opinion on the nominee.
(n) :
(US politics) In the House of Representatives, a rejection slip given to tax and spending bills sent to it by the Senate that did not originate in the House, per the House's interpretation of the Origination Clause.
(n) :
(US politics) In the Senate, the slip on which the senators from the state of residence of a federal judicial nominee give an opinion on the nominee.
(n) :
(US politics) In the House of Representatives, a rejection slip given to tax and spending bills sent to it by the Senate that did not originate in the House, per the House's interpretation of the Origination Clause.