During a teacher's class. This is what the teacher(confidence) endures

In the course of my speech, a term eludes me and I used the word "whatchamacallit". Everyone burst into laughter whiles repeating the word "whatchamacallit". I knew what they thought. I asked, "where from the laughter?". "Whatchamacallit", one of them in uncontrollable laughter repeated the word again! I waited patiently for the outburst to wane.

I requested for a dictionary. I was handed one of the thumb index series. In a split of a second I was there: WHATCHAMACALLIT. I gave it to one of them to read. It reads: 

"Whatchamacallit - used to refer to a person or thing whose name one cannot recall, does not know, or does not wish to specify." 

Examples: 
1. John and whatchamacallit were here for dinner. (The second person's name cannot be recalled or forgotten). 
2. You left your whatchamacallit on the table. (The speaker may not know the name of the item). 
3. The leader of the opposition party, whatchamacallit lost the elections convincingly. (The speaker does not want to specify the name). 

The word sounds funny and appears more like a tongue-twister. So, pardon listeners if they burst into laughter in the course of using WHATCHAMACALLIT. It synonyms sound funny as well: They include dingus, thingamabob, thingamajig etc