The Collaborative International Dictionary of English v.0.48:

Alkaline \Al"ka*line\ (?; 277), a. [Cf. F. alcalin.]
   Of or pertaining to an alkali or to alkalies; having the
   properties of an alkali.
   [1913 Webster]

   Alkaline earths, certain substances, as lime, baryta,
      strontia, and magnesia, possessing some of the qualities
      of alkalies.

   Alkaline metals, potassium, sodium, c[ae]sium, lithium,
      rubidium.

   Alkaline reaction, a reaction indicating alkalinity, as by
      the action on limits, turmeric, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

alkaline
    adj 1: relating to or containing an alkali; having a pH greater
           than 7; "alkaline soils derived from chalk or limestone"
           [syn: alkaline, alkalic] [ant: acidic,
           amphiprotic, amphoteric]