excessive, overflow, spread out
濫 centers on water going beyond its proper limits: overflowing, spreading out uncontrollably, or becoming excessive. The idea of excess applies naturally to both physical overflow and abstract overindulgence.
濫 combines 氵 (water) with 監, which likely contributes both sound and the idea of looking or overseeing. The compound suggests water that is not contained, as if it has overflowed its bounds while being watched.
Water 氵 is being watched 監, but it overflows anyway. Picture a dam inspector watching helplessly as water spreads out beyond control.
For ラン, imagine a LAN party where too many people show up and the room overflows with gamers: LAN -> ラン, and the crowd spreads out excessively.
overflowing; flood; inundation; deluge
overproduction; careless manufacture; churning out (substandard goods)
flooding within the confines of a levee (i.e. caused by surface runoff, drainage failure, etc.)
flooding caused by overflowing of rivers (e.g. breaching levee banks)
abuse of rights; improper use of a privilege
flood plain
flooding caused by overflowing of rivers (e.g. breaching levee banks)
morally corrupt
morally corrupt; slovenly; obscene
source; beginning; origin
excessive or unreasonable legal action; vexatious litigation
mass production of inferior goods