What is a Waiting Word™?

Question

_{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.}

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If a word conforms to a special rule I call it a Waiting Word™. Use the examples below to find the rule.

$$\begin{array}{|c|c|}\hline \bbox[yellow]{\textbf{Waiting Words™}} & \bbox[yellow]{\textbf{Not Waiting Words™}}\\\hline \text{AN} & \text{A}\\\hline \text{FEEL} & \text{TOUCH}\\\hline \text{FOOTSTOOL} & \text{STOOL}\\\hline \text{GNAW} & \text{CHEW}\\\hline \text{MOM} & \text{DAD}\\\hline \text{OUTDO} & \text{OUTLAST}\\\hline \text{POP} & \text{SNAP}\\\hline \text{ROTOR} & \text{WHEEL}\\\hline \text{SEXES} & \text{GENDERS}\\\hline \text{SIS} & \text{BRO}\\\hline \text{TAINT} & \text{DEFILE}\\\hline \end{array}$$

CSV version:

Waiting Words™,Not Waiting Words™
AN,A
FEEL,TOUCH
FOOTSTOOL,STOOL
GNAW,CHEW
MOM,DAD
OUTDO,OUTLAST
POP,SNAP
ROTOR,WHEEL
SEXES,GENDERS
SIS,BRO
TAINT,DEFILE

Answer 1

A Waiting Word™ is...

a palindrome (including spaces) in Morse code.

    AN       :  .- -.
    FEEL     :  ..-. . . .-..
    FOOTSTOOL:  ..-. --- --- - ... - --- --- .-..
    GNAW     :  --. -. .- .--
    MOM      :  -- --- --
    POP      :  .--. --- .--.
    ROTOR    :  .-. --- - --- .-.
    SEXES    :  ... . -..- . ...
    SIS      :  ... .. ...
    TAINT    :  - .- .. -. -