All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Literally, Tajweed means beautification. The Arabs say Jawwada (verb) something, i.e. beautify it. The Arabs also use Tajweed to mean doing something in a perfect way. When somebody Jawwada something, he does it in the best way and with the best quality.
But the term Tajweed used in the sciences of Quran is of two kinds:
1) Knowledge of the rules of recitation set up by the scholars of Tajweed. This is called the theorical Tajweed.
2) The second type of Tajweed is the practical one, which means: saying each letter with its right mode of articulation and in its right place of articulation.
Allah knows best.