Un certificado de depósito a término (CDT):

"Es un título valor expedido por una entidad financiera por el depósito de una suma de dinero a un plazo y a una tasa determinada. Los plazos pueden ser de 30 días en adelante, siendo los más comunes los de 30, 60, 90, 180 y 360 días. Instrumento de inversión de renta fija que puede negociarse en el mercado secundario de la bolsa de valores, pero que no es redimible sino hasta su vencimiento."
http://www.serfinco.com/products/rent/cdt.asp
also: http://www.businesscol.com/productos/glosarios/economico/glo...

i.e. "They are different from savings accounts in that the CD has a specific, fixed term (often three months, six months, or one to five years), and, usually, a fixed interest rate. It is intended that the CD be held until maturity, at which time the money may be withdrawn together with the accrued interest."
http://en.wikipedia.org/wiki/Certificate_of_deposit

A depósito a término is simply a term deposit:
"A deposit held at a financial institution that has a fixed term. These are generally short-term with maturities ranging anywhere from a month to a few years. When a term deposit is purchased, the lender (the customer) understands that the money can only be withdrawn after the term has ended or by giving a predetermined number of days notice."
http://investopedia.com/terms/t/termdeposit.asp

Suerte!