Which term is associated with something that is troubling or adverse?

The term "untoward" is associated with something that is troubling or adverse. This word is often used to describe circumstances or events that are unexpected and have negative or unfavorable connotations. The essence of "untoward" lies in its implications of difficulties or complications that arise, making it suitable to indicate situations that are problematic or undesirable.

In contrast, "ubiquitous" means being present everywhere at once and does not imply any negative context. "Urbane" refers to someone who is sophisticated and polished in manner, which also carries a positive connotation. The term "vacillate" indicates a state of indecision or fluctuation between choices and does not inherently express trouble or adversity. Thus, "untoward" stands out as the accurate term for describing something troubling or adverse.