A K-7 teacher vs. me

I questioned about the definition of the word "lurk", she answered two of these three:
1 a : to lie in wait in a place of concealment especially for an evil purpose b : to move furtively or inconspicuously c : to persist in staying
2 a : to be concealed but capable of being discovered; specifically : to constitute a latent threat b : to lie hidden

(3 : to read messages on an Internet discussion forum (as a newsgroup or chat room) without contributing)

— lurk·er noun

synonyms lurk, skulk, slink, sneak mean to behave so as to escape attention. lurk implies a lying in wait in a place of concealment and often suggests an evil intent . skulk suggests more strongly cowardice or fear or sinister intent . slink implies moving stealthily often merely to escape attention . sneak may add an implication of entering or leaving a place or evading a difficulty by furtive or underhanded methods .

Then I asked her to define the word "mass" in a new way. She had no idea.