Correct spelling for the English word "sader" is [sˈe͡ɪdə], [sˈeɪdə], [s_ˈeɪ_d_ə] (IPA phonetic alphabet).
Apologies, but "sader" does not have an existing dictionary definition. It is possible that you may have misspelled the word or it could be a rare or region-specific term that is not widely recognized. A comprehensive dictionary typically includes terms that have established usage and recognition across a broad range of domains and contexts.
If you were referring to the word "sadder," then its dictionary definition is as follows:
Sadder (comparative of the adjective "sad") is an English word that indicates a greater degree of sadness or sorrow. It is used to describe a feeling or state of mind that is more intense than just feeling sad. It is often employed to express a deeper level of emotional or mental anguish that accompanies a loss, a disappointment, or a tragic event. Sadder can also signify a sense of melancholy or a general downcast mood. The word is primarily used within the context of human emotions, referring to the subjective experience of sadness. Its comparative form, "sadder," demonstrates an amplification or increase in the degree of sadness being conveyed.