VERB (3)

1. join letters in a ligature when writing;

2. bind chemically;
- Example: "The enzyme ligated"

3. bind with a bandage or ligature;
- Example: "ligate the artery"

The Collaborative International Dictionary of English v.0.48:

Ligate \Li"gate\ (l[imac]"g[=a]t), v. t. [L. ligatus, p. p. of
   ligare.]
   1. To tie with a ligature; to bind around; to bandage.
      [1913 Webster]

   2. (Molecular biology) To concatenate two strands of (nucleic
      acid, usually DNA), in an end-to-end fashion, using a
      ligase.
      [PJC]

WordNet (r) 3.0 (2006):

ligate
    v 1: join letters in a ligature when writing
    2: bind chemically; "The enzyme ligated"
    3: bind with a bandage or ligature; "ligate the artery"