如果你想表达一个单词是假的或不存在的，你可以使用以下表达方式之一：

"That word is fake."
"That word is not a real word."
"That word is made up."
"That word is a fabrication."

你也可以使用诸如 "nonexistent" 或 "fictitious" 等形容词来描述假的单词。例如：

"That word is nonexistent."
"That word is fictitious."

希望这些信息对你有帮助！