This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles.
If a word satisfies a certain property, it is called a Ping Pong Word™. Find out what the rule is given the following examples.
$$ % set Title text. (spaces around the text ARE important; do not remove.) % increase Pad value only if your entries are longer than the title bar. % \def\Pad{\P{0.0}} \def\Title{\textbf{ Ping Pong }} % \def\S#1#2{\Space{#1}{20px}{#2px}}\def\P#1{\V{#1em}}\ \def\V#1{\S{#1}{9}} \def\T{\Title\textbf{Words }^™\Pad}\def\NT{\Pad\textbf{Not}\T\ }\displaystyle \smash{\lower{29px}\bbox[yellow]{\phantom{\rlap{rubio.2017.02.04}\S{6px}{0} \begin{array}{cc}\Pad\T&\NT\\\end{array}}}}\atop\def\V#1{\S{#1}{5}} \begin{array}{|c|c|}\hline\Pad\T&\NT\\\hline % \text{DUCK}&\text{GOOSE}\\ \hline \text{VISUAL}&\text{OPTICAL}\\ \hline \text{CORNFIELD}&\text{PUMPKIN}\\ \hline \text{QUANTITY}&\text{QUALITY}\\ \hline \text{NEIGHBOR}&\text{FRIEND}\\ \hline \text{WORLD}&\text{EARTH}\\ \hline \text{TURKEY}&\text{CHICKEN}\\ \hline \text{EIGHT}&\text{NINE}\\ \hline \text{ENCHANTMENT}&\text{WITCHCRAFT}\\ \hline \end{array}$$
