St Agnes's flower noun

The snowflake (qv under snow¹)

St Andrew's cross noun

1. A cross in the form of the letter X
2. A white cross of this type on a blue background, as borne on the banner of Scotland

St Andrew's Day noun

30 November

St Anthony's cross noun

The tau cross, a cross shaped like the Greek letter T

St Anthony's fire noun

1. Prob an old name for ergotism
2. See under Anthony

St Barbara's cress noun

Yellow rocket

St Barnaby's thistle noun

A knapweed flowering about the saint's day (11 June)

St Bernard's dog or St Bernard noun

A breed of very large dog, named after the hospice of the Great St Bernard on the Swiss–Italian border, used, esp formerly, to rescue travellers lost in the snow

St Crispin's Day noun

A shoemakers' festival, 25 October

St Cuthbert's beads, St Cuthbert's duck see under Cuthbert

St Dabeoc's heath noun

A rare Irish shrub (genus Daboecia)

St David's Day noun

1 March

St Elmo's fire noun

An electrical charge forming a glow around a church spire, ship's mast, etc, a corposant

St George's cross noun

A red upright cross on a white background

St George's Day noun

23 April

St Hubert's disease noun

Another name for hydrophobia

St Ignatius's bean noun

The poisonous seed of a plant (Strychnos ignatii) related to nux vomica

St James's noun

The British royal court

St John's bread noun

Another name for the carob bean

St John's Day noun

27 December

St Johnston's ribbon or St Johnston's tippet noun

The hangman's rope (St Johnston or St John's toun being Perth, associated in the 18c with hangings)

St John's wort noun

Any of the plants of the Hypericum genus

St Julien noun

An esteemed red Bordeaux wine from the Médoc region

St Leger noun

A horse race run annually at Doncaster, so called since 1778 from Colonel St Leger

St Luke's summer noun

A spell of pleasant weather about the middle of October

St Martin's evil noun

Drunkenness

St Martin's summer noun

A spell of mild, damp weather in late autumn

St Nicholas's clerks plural noun

Thieves

St Patrick's Day noun

17 March

St Peter's fish noun

A name applied to several fish, eg the dory and the tilapia

St Peter's wort noun

1. Square-stalked St John's wort
2. Extended to several other plants

St Stephen's noun

The Houses of Parliament

St Stephen's Day noun

26 December

St Swithin's Day noun

15 July

St Tibb's Eve, St Tib's Eve, Tib's Eve or Tibb's Eve noun

Never

St Trinian adjective

1. Of, relating to or typical of St Trinian's
2. Applied to or denoting unruly or riotous behaviour, exploits, or spectacularly untidy dress, usu of schoolgirls (informal)

noun

A pupil of St Trinian's

St Trinian's noun

A fictitious girls' school created by the English cartoonist Ronald Searle (1920-2011) and popularized in humorous films

St Valentine's Day noun

14 February (see also under valentine)

St Vitus's dance noun

A non-technical name for Sydenham's chorea