The Collaborative International Dictionary of English v.0.48:

Testimonial \Tes`ti*mo"ni*al\, n. [Cf. OF. testimoniale, LL.
   testimonialis, L. testimoniales (sc. litterae). See
   Testimonial, a.]
   1. A writing or certificate which bears testimony in favor of
      one's character, good conduct, ability, etc., or of the
      value of a thing.
      [1913 Webster]

   2. Something, as money or plate, presented to a preson as a
      token of respect, or of obligation for services rendered.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Testimonial \Tes`ti*mo"ni*al\, a. [L. testimonialis: cf. F.
   testimonial.]
   Relating to, or containing, testimony.
   [1913 Webster]

WordNet (r) 3.0 (2006):

testimonial
    adj 1: expressing admiration or appreciation; "testimonial
           dinner"
    2: of or relating to or constituting testimony
    n 1: something that serves as evidence; "his effort was
         testimony to his devotion" [syn: testimony,
         testimonial]
    2: something given or done as an expression of esteem [syn:
       tribute, testimonial]
    3: something that recommends (or expresses commendation of) a
       person or thing as worthy or desirable [syn:
       recommendation, testimonial, good word]