使役受身（〜させられる）
To be made to do…machine translation
FormationGroup I: う-row → あ-row + される (す-ending verbs: 〜させられる); group II: drop る + させられる; する → させられる、来る → 来させられる
The causative-passive expresses "being made to do something" — seen from the side of the person being ordered around, almost always with a feeling of reluctance or annoyance: 野菜を食べさせられました (I was made to eat vegetables), 一時間も待たされました (I was made to wait a whole hour). The person who makes you do it takes the particle に.
The conjugation is the causative carried over into the passive. Group I: change the final sound from the う-row to the あ-row and add される (the common contracted form): 待つ → 待たされる, 言う → 言わされる; verbs ending in す only have the long form させられる: 話す → 話させられる. Group II: drop る and add させられる: 食べる → 食べさせられる. Group III: する → させられる, 来る → 来させられる (こさせられる). The long form 〜せられる (待たせられる) for group I is also correct but less common.
A comparison to make the viewpoint clear: 母は私に野菜を食べさせた (my mother made me eat vegetables — from the mother's side) ↔ 私は母に野菜を食べさせられた (I was made to eat vegetables by my mother — from my side, with the sense "I didn't want to"). If the thing you're asked to do isn't unpleasant, Japanese speakers use the plain causative or 〜てもらう instead of this pattern.
Examples
子どものとき、母に野菜を食べさせられました。
When I was a child, my mother made me eat vegetables.
会議で意見を言わされました。
I was made to give my opinion at the meeting.
友達に一時間も待たされました。
My friend kept me waiting a whole hour.