[F à plomb according to the plummet, i.e., straight up and down, vertical position]
1. imperturbable self-possession, poise, or assurance.
2. the perpendicular, or vertical, position.
composure, equanimity, imperturbability.
"He was the guy you could send to any story, at any time and he handled it capably, calmly, credibly and with total aplomb"