A string of letters that spells one word forward and another word backwards.
Example: stressed and desserts.
Also #14, #16 and (#17 not sure) are common german words. Why not stick to one language.
#4 and #18 are "reversed" but the meaning ist different, #4 different words, #18 same words
not the first german words in the english dictionary: kindergarten, iceberg (in german Eisberg), doppelganger (in german: Doppelgänger)