https://eow.alc.co.jp/search?q=喪服
burial vestments
mourning attire
mourning clothes
mourning dress

https://en.wikipedia.org/wiki/Mourning
East Asia
The Japanese term for mourning dress is mofuku (喪服), referring to either primarily black Western-style formal wear or to black kimono and traditional clothing worn at funerals and Buddhist memorial services. Other colors, particularly reds and bright shades, are considered inappropriate for mourning dress. 
...
Men's mourning dress consists of clothing worn on extremely formal occasions: a plain black silk five-crested kimono and black and white, or gray and white, s

"mourning dress" is ambiguous in English.  (i.e. is this limited to a woman's article of clothing? no)

@@ -17,0 +18,2 @@
+<gloss>mourning clothes</gloss>
+<gloss>mourning attire</gloss>