Simply, depends on intent and whether or not the trust and understood rules between you and your S/O were broken.
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CHEAT
[cheet]
-verb (used with object)
1.
to defraud; swindle: He cheated her out of her inheritance.
2.
to deceive; influence by fraud: He cheated us into believing him a hero.
3.
to elude; deprive of something expected: He cheated the law by suicide.
–verb (used without object)
4.
to practice fraud or deceit: She cheats without regrets.
5.
to violate rules or regulations: He cheats at cards.
6.
to take an examination or test in a dishonest way, as by improper access to answers.
–noun
7.
a person who acts dishonestly, deceives, or defrauds: He is a cheat and a liar.
8.
a fraud; swindle; deception: The game was a cheat.
9.
Law. the fraudulent obtaining of another’s property by a pretense or trick.
10.
an impostor: The man who passed as an earl was a cheat.
Origin:
1325–75; ME chet (n.) (aph. for achet, var. of eschet escheat); cheten to escheat, deriv. of chet (n.)
—Related forms
cheat·a·ble, adjective
cheat·ing·ly, adverb
outcheat, verb (used with object)
un·cheat·ed, adjective
un·cheat·ing, adjective
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If boob fondling is included in you and your S/O’s understood no-nos, then yes, you cheated. If both parties are fully informed and accept this conduct, then no, that is not cheating.