Designated terminal element

Designated terminal element is a in a tree the designated terminal element (DTE) is that terminal element in a given constituent that is exclusively dominated by strong nodes; it is the most prominent element of a given constituent.

Example
in the English word achromatic the syllable -ma- is the designated terminal element:

/ \ 	 w   s  	 / \  /\ s  w s w 	achromatic

Link
Utrecht Lexicon of Linguistics