This is the 1859th most frequent French word.
lourde
Heavy.
Here, 'lourde' is used as an adjective to describe the physical weight of the box.
Cette boîte est trop lourde pour moi à porter.
This box is too heavy for me to carry.
In this case, 'lourde' describes the metaphorical weight or complexity of the conversation.
La conversation était lourde et difficile à suivre.
The conversation was heavy and difficult to follow.
Here, 'lourde' refers to the emotional weight or significance of the responsibility felt.