
Adulterous
Negative Connotation
The word 'adulterous' often carries a strong negative judgment and is considered highly critical. 
Literal Use
Use 'adulterous' literally to describe actions that directly involve marital infidelity, not metaphorically. 
Serious Tone
'Adulterous' is a serious term that's not used in a casual or joking context because of its weighty subject. 