If it's just one long cell, or if all the long cells are in a column, you could try using the "Text to Columns" feature (under the Data tab of the Ribbon). If you set it to be delimited by space (assuming your words are separated by spaces), this will make it so that each word occupies its own cell. Then when you use Find, it will highlight the exact cell.
Another option would be to copy the range you want to search and paste into MS Word. From there, you can search, and it will highlight the exact word.