The Collaborative International Dictionary of English v.0.48:

Last \Last\ (l[.a]st), a. [OE. last, latst, contr. of latest,
   superl. of late; akin to OS. lezt, lazt, last, D. laatst, G.
   letzt. See Late, and cf. Latest.]
   1. Being after all the others, similarly classed or
      considered, in time, place, or order of succession;
      following all the rest; final; hindmost; farthest; as, the
      last year of a century; the last man in a line of
      soldiers; the last page in a book; his last chance.
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            Also day by day, from the first day unto the last
            day, he read in the book of the law of God. --Neh.
                                                  viii. 18.
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            Fairest of stars, last in the train of night.
                                                  --Milton.
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   2. Next before the present; as, I saw him last week.
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   3. Supreme; highest in degree; utmost.
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            Contending for principles of the last importance.
                                                  --R. Hall.
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   4. Lowest in rank or degree; as, the a last place finish.
      --Pope.
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   5. Farthest of all from a given quality, character, or
      condition; most unlikely; having least fitness; as, he is
      the last person to be accused of theft.
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   At last, at the end of a certain period; after delay. "The
      duke of Savoy felt that the time had at last arrived."
      --Motley.

   At the last. [Prob. fr. AS. on l[=a]ste behind, following
      behind, fr. l[=a]st race, track, footstep. See Last mold
      of the foot.] At the end; in the conclusion. [Obs.] "Gad,
      a troop shall overcome him; but he shall overcome at the
      last." --Gen. xlix. 19.

   Last heir, the person to whom lands escheat for lack of an
      heir. [Eng.] --Abbott.

   On one's last legs, at, or near, the end of one's
      resources; hence, on the verge of failure or ruin,
      especially in a financial sense. [Colloq.]

   To breathe one's last, to die.

   To the last, to the end; till the conclusion.
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            And blunder on in business to the last. --Pope.

   Syn: At Last, At Length.

   Usage: These phrases both denote that some delayed end or
          result has been reached. At length implies that a long
          period was spent in so doing; as, after a voyage of
          more than three months, we at Length arrived safe. At
          last commonly implies that something has occurred (as
          interruptions, disappointments, etc.) which leads us
          to emphasize the idea of having reached the end; as,
          in spite of every obstacle, we have at last arrived.
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The Collaborative International Dictionary of English v.0.48:

At \At\, prep. [AS. [ae]t; akin to OHG. az, Goth., OS., & Icel.
   at, Sw. [*a]t, Dan. & L. ad.]
   Primarily, this word expresses the relations of presence,
   nearness in place or time, or direction toward; as, at the
   ninth hour; at the house; to aim at a mark. It is less
   definite than in or on; at the house may be in or near the
   house. From this original import are derived all the various
   uses of at. It expresses:
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   1. A relation of proximity to, or of presence in or on,
      something; as, at the door; at your shop; at home; at
      school; at hand; at sea and on land.
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   2. The relation of some state or condition; as, at war; at
      peace; at ease; at your service; at fault; at liberty; at
      risk; at disadvantage.
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   3. The relation of some employment or action; occupied with;
      as, at engraving; at husbandry; at play; at work; at meat
      (eating); except at puns.
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   4. The relation of a point or position in a series, or of
      degree, rate, or value; as, with the thermometer at
      80[deg]; goods sold at a cheap price; a country estimated
      at 10,000 square miles; life is short at the longest.
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   5. The relations of time, age, or order; as, at ten o'clock;
      at twenty-one; at once; at first.
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   6. The relations of source, occasion, reason, consequence, or
      effect; as, at the sight; at this news; merry at anything;
      at this declaration; at his command; to demand, require,
      receive, deserve, endure at your hands.
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   7. Relation of direction toward an object or end; as, look at
      it; to point at one; to aim at a mark; to throw, strike,
      shoot, wink, mock, laugh at any one.
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   At all, At home, At large, At last, At length, At
   once, etc. See under All, Home, Large, Last (phrase
      and syn.), Length, Once, etc.

   At it, busily or actively engaged.

   At least. See Least and However.

   At one. See At one, in the Vocabulary.
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   Syn: In, At.

   Usage: When reference to the interior of any place is made
          prominent in is used. It is used before the names of
          countries and cities (esp. large cities); as, we live
          in America, in New York, in the South. At is commonly
          employed before names of houses, institutions,
          villages, and small places; as, Milton was educated at
          Christ's College; money taken in at the Customhouse; I
          saw him at the jeweler's; we live at Beachville. At
          may be used before the name of a city when it is
          regarded as a mere point of locality. "An English king
          was crowned at Paris." --Macaulay. "Jean Jacques
          Rousseau was born at Geneva, June, 28, 1712." --J.
          Morley. In regard to time, we say at the hour, on the
          day, in the year; as, at 9 o'clock, on the morning of
          July 5th, in the year 1775.
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WordNet (r) 3.0 (2006):

at last
    adv 1: as the end result of a succession or process; "ultimately
           he had to give in"; "at long last the winter was over"
           [syn: ultimately, finally, in the end, at last,
           at long last]