The Collaborative International Dictionary of English v.0.48:

Maximum \Max"i*mum\, n.; pl. Maxima. [L., neut. from maximus
   the greatest. See Maxim.]
   The greatest quantity or value attainable in a given case;
   or, the greatest value attained by a quantity which first
   increases and then begins to decrease; the highest point or
   degree; -- opposed to minimum.
   [1913 Webster]

         Good legislation is the art of conducting a nation to
         the maximum of happiness, and the minimum of misery.
                                                  --P.
                                                  Colquhoun.
   [1913 Webster]

   Maximum thermometer, a thermometer that registers the
      highest degree of temperature attained in a given time, or
      since its last adjustment.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Maximum \Max"i*mum\, a.
   Greatest in quantity or highest in degree attainable or
   attained; as, a maximum consumption of fuel; maximum
   pressure; maximum heat.
   [1913 Webster]

WordNet (r) 3.0 (2006):

maximum
    adj 1: the greatest or most complete or best possible; "maximal
           expansion"; "maximum pressure" [syn: maximal,
           maximum] [ant: minimal, minimum]
    n 1: the largest possible quantity [syn: maximum, upper
         limit] [ant: lower limit, minimum]
    2: the greatest possible degree; "he tried his utmost" [syn:
       utmost, uttermost, maximum, level best]
    3: the point on a curve where the tangent changes from positive
       on the left to negative on the right [ant: minimum]