Definitions of endocrine gland on the Web:

• any of the glands of the endocrine system that secrete hormones directly into the bloodstream
  wordnetweb.princeton.edu/perl/webwn

• A group of specialized cells that release hormones into the blood. For example, the islets in the pancreas, which secrete insulin, are endocrine glands.
  www.caninsulin.com/glossary.asp

• an organ producing hormones.
  www.duofertility.com/glossary

• (en'do-krin) An organ that manufactures hormones and sends them out into the bloodstream.
  www.sex-ed101.org/glossary.html

• A ductless, hormone-producing gland that is part of the endocrine system.
  schools.look4.net.nz/science/biology/human/glossary2/

• A ductless gland, eg, the thyroid or the pituitary glands, which produces one or more hormones which will be released into the bloodstream to be distributed body wide in order to interact with their target cells, tissues, and organs.
  www.apsu.edu/thompsonj/Anatomy%20&%20Physiology/2010/2010%20Exam%20Reviews/Exam%205%20Final%20Review/CH%2016%20General%20Endocrine%20Terminology.htm