泛滥 literally combines 泛 (fàn), meaning 'to spread widely' or 'to overflow', and 滥 (làn), meaning 'excessive' or 'uncontrolled'. Together, they form a verb describing an uncontrolled, excessive spreading—like water flooding beyond its banks, or something undesirable proliferating rapidly. While originally used for natural floods, it’s now commonly extended metaphorically to describe unchecked growth or proliferation: invasive species, misinformation, low-quality products, or even emotions like anxiety.

This word carries a distinctly negative connotation—it implies harm, loss of control, or disruption of balance. It often appears in formal writing, news reports, and environmental or social commentary. You’ll frequently see it in phrases like ‘泛滥成灾’ (fàn làn chéng zāi, 'flooding turns into disaster') or ‘信息泛滥’ (xìnxī fàn làn, 'information overload'). It is rarely used in neutral or positive contexts, and never for intentional, beneficial expansion.