How to spell EXTREMER correctly?

The correct spelling for "extremer" is actually "more extreme". Many people mistakenly use "extremer" to convey a higher level of extremity. However, in English, we use the structure "more + adjective" to indicate comparative degrees. Therefore, using "more extreme" would be the appropriate suggestion.

• extreme The athletes performed extreme stunts that left the audience in awe.
• extremely I am extremely excited for my upcoming vacation to Europe.
• extremes The weather conditions here can fluctuate between extremes.

Intertubing

• antedating
• entertain
• entertainer
• entertaining
• inditing
• inner-tubing
• intertwine
• interurban
• intuiting
• undertaking