Princeton's WordNet

1. liter, litre, l, cubic decimeter, cubic decimetre(noun)

   a metric unit of capacity, formerly defined as the volume of one kilogram of pure water under standard conditions; now equal to 1,000 cubic centimeters (or approximately 1.75 pints)

   Synonyms:
   litre, lambert, fifty, cubic decimeter, liter, cubic decimetre, l

   Antonyms:
   ordinal

2. fifty, 50, L(noun)

   the cardinal number that is the product of ten and five

   Synonyms:
   litre, lambert, fifty, liter, fifty dollar bill, cubic decimetre, cubic decimeter

   Antonyms:
   ordinal

3. lambert, L(noun)

   a cgs unit of illumination equal to the brightness of a perfectly diffusing surface that emits or reflects one lumen per square centimeter

   Synonyms:
   litre, lambert, fifty, cubic decimeter, liter, cubic decimetre

   Antonyms:
   ordinal

4. L, l(adj)

   the 12th letter of the Roman alphabet

   Synonyms:
   litre, lambert, fifty, cubic decimeter, liter, cubic decimetre

   Antonyms:
   ordinal

5. fifty, 50, l(adj)

   being ten more than forty

   Synonyms:
   fifty, l

   Antonyms:
   ordinal