Which version of PPT are you using?
If you are using 2002 or later, you can set up a pair of triggered
animations to do this. Give the definition box an entrance animation and an
exit animation. Place a box with no line and 98% fill over the word. Right
click the entrance animation and select timing. Change the radio button from
"as part of a timed sequence" to "triggered". From the drop down box that
appears, select the empty box you just created. OK your way out. Repeat the
process for the exit animation, but have the trigger be the box containing
the definition.
If you are using one of the earlier versions, you will need to set up a
hyperlink to another slide that shows the box and then a hyperlink back to
the original slide to hide it.
--
Kathryn Jacobs, Microsoft MVP PowerPoint and OneNote
Author of Kathy Jacobs on PowerPoint - Available now from Holy Macro! Books
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I believe life is meant to be lived. But:
if we live without making a difference, it makes no difference that we lived