English translations of chasid often employ terms such as "pious" and "devout", which do not do full justice to the word.
Hillel (Avot 2:6) states that an am ha'aretz cannot be a chasid. But what is an am ha'aretz? Unlike chasid -- which is a term of praise -- am ha'aretz is almost always a pejorative term. It is often rendered "ignoramus", "unlearned person", someone who is "common" or "knows not Torah".
Over the years, Hillel's statement has attracted many comments and has been applied to many situations. I have just found another one.
The priestly blessings that the Kohanim administer to a Jewish prayer quorum are a practice of great antiquity, going right back to biblical times (see Numbers 6:22-27). By long-established custom and practice, the congregation do not stare at the Kohanim at the point of delivery of these blessings, but avert their gaze while they listen intently to the Kohanim's words.
Rabbi Eliezer Papo (the 'Pele Yo'etz') in his book Chesed La'Alafim (vol 1, 128:16) notes that some people, in an excess of piety, do not merely avert their eyes from their priestly benefactors but actually turn their backs on them -- presumably to avoid any risk of inadvertently looking up at the Kohanim and watching them at work. Since all a person need do is to cast his or her gaze demurely down to the ground, this act of turning one's back on the Kohanim is a demonstration of an excess of piety -- and this constitutes the behaviour of an am ha'aretz. And that, concludes the Pele Yo'etz, is a practical example of Hillel's teaching that an am ha'aretz cannot be a chasid.
