Done by one side alone, when more than one side is involved in the situation — and, importantly, without asking or agreeing with the others. A unilateral decision is one you made by yourself about something that affects other people too. A unilateral ceasefire is when one army stops shooting whether or not the other one does. This is a word from news and politics: unilateral action, a unilateral withdrawal, a unilateral decision to raise prices. It sits in a small family with bilateral (two sides, both agreeing — a bilateral trade deal) and multilateral (many sides together). Watch the tone. Unilateral is officially neutral — it only describes how many sides acted — but in practice it usually carries a frown. When a reporter says a country acted unilaterally, they are often hinting that it ignored its partners, or that it was arrogant. If the speaker approves, they are more likely to say decisive or independent. It also appears in medicine with a plainer meaning: on one side of the body only, as in unilateral hearing loss — deafness in just one ear. No criticism there at all.