deceased spousal unused exclusion amount
(4) Deceased spousal unused exclusion amount For purposes of this subsection, with respect to a surviving spouse of a deceased spouse dying after December 31, 2010 , the term “deceased spousal unused exclusion amount” means the lesser of— (A) the basic exclusion amount, or (B) the excess of— (i) the applicable exclusion amount of the last such deceased spouse of such surviving spouse, over (ii) the amount with respect to which the tentative tax is determined under section 2001(b)(1) on the estate of such deceased spouse.