• hw,
• hom,
• ryhm,
• hhom,
• hmph,
• htm,
• rhym,
• johm,
• hx,
• om,
• hmm,
• qm,
• uhm,
• thmb,
• hme,
• hk,
• hy,
• chx,
• hdmi,
• mhmm

• ham,
• n.m.,
• hi,
• Ht.,
• Him,
• ha,
• cm,
• hmo,
• a.m.,
• M,
• m.,
• h's,
• p.m.,
• H,
• mm,
• nm,
• hem,
• hum,
• AM,
• hg,
• he.

The plural form of "hm" is "hms"

The singular form of the word "hm" remains "hm".