squishy
In a video game - a character or enemy that has low defense and is likely an easy kill for enemies. Note that the term refers to character's own defenses, not controlling player being bad at surviving on it.

In online gaming the term is usually used when someone who should've picked a character with solid defenses (like a "tank") picked a "squish" character instead.
Great, this jackass picks squishy Teemo top and now we have no tank! GG, report this troll!