'Teen Mom' Star Jenelle Evans -- ARRESTED ... For Cussing in Public

"Teen Mom" star Jenelle Evans' potty mouth got her locked up in South Carolina yesterday ... after cops tried muzzling her during an argument with her boyfriend and she refused.

Police were dispatched 2 separate times to Evans' home yesterday -- both times for loudly arguing with her boyfriend outside ... according to reports.

Cops say Jenelle's BF told them the MTV star locked him out of the house during an argument ... but he agreed to go for a walk and cool off -- so officers left.

Shortly after, they were dispatched again ... and reportedly found her boyfriend had climbed in the house through a window -- which caused Jenelle to lock herself inside the bathroom.

Police handled the situation before attempting to leave -- but Janelle started yelling cuss words outside the house ... and when she refused to stop they took her into custody for "breach of the peace."

Worst part ... Janelle is still on probation -- meaning she could be facing additional jail time if convicted.

Janelle was only in jail for about an hour.